THE

RAY SOCIETY.

INSTITUTED MDCCCXLIV.

LONDON.

MDCCCLI.

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A MONOGRAPH

ON THE SUB-CLASS

CIRRIPEDIA,

WITH

FIGURES OF ALL THE SPECIES.

BY

CHARLES DARWIN, F.R.S., F.G.S.

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THE LEPADIDÆ;

OR,

PEDUNCULATED CIRRIPEDES.

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LONDON:

PRINTED FOR THE RAY SOCIETY.
MDCCCLI.

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C. AND J. ADLARD, PRINTERS, BARTHOLOMEW[Pg v]

PREFACE.

My duty, in acknowledging the great obligations
under which I lie to many naturalists, affords me most
sincere pleasure. I had originally intended to have
described only a single abnormal Cirripede, from the
shores of South America, and was led, for the sake of
comparison, to examine the internal parts of as many
genera as I could procure. Under these circumstances,
Mr. J. E. Gray, in the most disinterested manner, suggested
to me making a Monograph on the entire class,
although he himself had already collected materials for
this same object. Furthermore, Mr. Gray most kindly
gave me his strong support, when I applied to the
Trustees of the British Museum for the use of the public
collection; and I here most respectfully beg to offer my
grateful acknowledgments to the Trustees, for their most
liberal and unfettered permission of examining, and when
necessary, disarticulating the specimens in the magnificent
collection of Cirripedes, commenced by Dr. Leach, and
steadily added to, during many years, by Mr. Gray.
Considering the difficulty in determining the species in
this class, had it not been for this most liberal permission
by the Trustees, the public collection would have been of[Pg vi]
no use to me, or to any other naturalist, in systematically
classifying the Cirripedes.

Previously to Mr. Gray suggesting to me the present
Monograph, Mr. Stutchbury, of Bristol, had offered to
intrust to me his truly beautiful collection, the fruit of
many years’ labour. At that time I refused this most
generous offer, intending to confine myself to anatomical
observations; but I have since accepted it, and still
have the entire splendid collection for my free use.
Mr. Stutchbury, with unwearied kindness, further supplied
me with fresh specimens for dissection, and with
much valuable information. At about the same period,
Mr. Cuming strongly urged me to take up the subject,
and his advice had more weight with me than that of
almost any other person. He placed his whole magnificent
collection at my disposal, and urged me to treat
it as if it were my own: whenever I told him that I
thought it necessary, he permitted me to open unique
specimens of great value, and dissect the included animal.
I shall always feel deeply honoured by the confidence
reposed in me by Mr. Cuming and Mr. Stutchbury.

I lie under obligations to so many naturalists, that I
am, in truth, at a loss how to express my gratitude.
Mr. Peach, over and over again, sent me fresh specimens
of several species, and more especially of Scalpellum
vulgare, which were of invaluable assistance to me in
making out the singular sexual relations in that species.
Mr. Peach, furthermore, made for me observations on
several living individuals. Mr. W. Thompson, the distinguished
Natural Historian of Ireland, has sent me the[Pg vii]
finest collection of British species, and their varieties,
which I have seen, together with many very valuable
MS. observations, and the results of experiments. Prof.
Owen procured for me the loan of some very interesting
specimens in the College of Surgeons, and has always
given me his invaluable advice and opinion, when consulted
by me. Professor E. Forbes has been, as usual,
most kind in obtaining for me specimens and information
of all kinds. To the Rev. R. T. Lowe I am indebted for
his particularly interesting collection of Cirripedes from
the Island of Madeira—a collection offering a singular
proof what treasures skill and industry can discover in
the most confined locality. The well-known conchologist,
Mr. J. G. Jeffreys, has sent for my examination a very
fine collection of British specimens, together with a
copious MS. list of synonyms, with the authorities
quoted. To the kindness of Messrs. M^c Andrew, Lovell
Reeve, G. Busk, G. B. Sowerby, Sen., D. Sharpe,
Bowerbank, Hancock, Adam White, Dr. Baird, Sir John
Richardson, and several other gentlemen, I am greatly
indebted for specimens and information: to Mr. Hancock
I am further indebted for several long and interesting
letters on the burrowing of Cirripedes.

Nor are my obligations confined to British naturalists.
Dr. Aug. Gould, of Boston, has most kindly transmitted to
me some very interesting specimens; as has Prof. Agassiz
other specimens collected by himself in the Southern
States. To Mr. J. D. Dana, I am much indebted for
several long letters, containing original and valuable information
on points connected with the anatomy of the[Pg viii]
Cirripedia. To Mr. Conrad I am likewise indebted for
information and assistance. Both the celebrated Professors,
Milne Edwards and Müller, have lent me, from the
great public collections under their charge, specimens which
I should not otherwise have seen. To Professor W. Dunker,
of Cassel, I am indebted for the examination of his whole
collection. I have, in a former publication, expressed my
thanks to Professor Steenstrup, but I must be permitted
here to repeat them, for a truly valuable present of a
specimen of the Anelasma squalicola of this work. I will
conclude my thanks to all the above British and foreign
naturalists, by stating my firm conviction, that if a person
wants to ascertain how much true kindness exists amongst
the disciples of Natural History, he should undertake, as I
have done, a Monograph on some tribe of animals, and
let his wish for assistance be generally known.

Had it not been for the Ray Society, I know not how
the present volume could have been published; and
therefore I beg to return my most sincere thanks to the
Council of this distinguished Institution. To Mr. G. B.
Sowerby, Junr., I am under obligations for the great
care he has taken in making preparatory drawings, and
in subsequently engraving them. I believe naturalists
will find that the ten plates here given are faithful delineations
of nature.

In Monographs, it is the usual and excellent custom to
give a history of the subject, but this has been so fully
done by Burmeister, in his ‘Beiträge zur Naturgeschichte
der Rankenfüsser,’ and by M. G. Martin St. Ange, in
his ‘Mémoire sur l’Organisation des Cirripèdes,’ that it[Pg ix]
would be superfluous here to repeat the same list of
authors. I will only add, that since the date, 1834, of
the above works, the only important papers with which
I am acquainted, are, 1st. Dr. Coldstream ‘On the
Structure of the Shell in Sessile Cirripedes,’ in the
‘Encyclopædia of Anatomy and Physiology;’ 2d. Dr.
Lovén ‘On the Alepas squalicola,’ (‘Ofversigt of Kongl.
Vetens.,’ &c. Stockholm, 1844, p. 192,) giving a short
but excellent account of this abnormal Cirripede; 3d.
Professor Leidy’s very interesting discovery, (‘Proceedings
of the Academy of Natural Sciences,’ Philadelphia,
vol. iv, No. I, Jan. 1848,) of eyes in a mature Balanus;
4th. Mr. A. Hancock’s Memoir, (‘Annals of Natural
History, 2d series, Nov. 1849,) on his Alcippe lampas,
the type of a new order of Cirripedes; 5th. Mr. Goodsir’s
Paper, (‘Edinburgh New Philosoph. Journal,’ July 1843,)
on the Larvæ in the First Stage of Development in
Balanus; 6th. Mr. C. Spence Bate’s valuable Paper on
the same subject, lately published, (Oct. 1851,) in the
‘Annals of Natural History;’ and lastly, M. Reinhardt
has described, in the ‘Copenhagen Journal of Natural
History, Jan. 1851,’ the Lithotrya nicobarica, and has
discussed its powers of burrowing into rocks.

I have given the specific or diagnostic characters, deduced
from the external parts alone, in both Latin and
English. As I found, during the progress of this work,
that a similarly abbreviated character of the softer internal
parts, was very useful in discriminating the species, I
have inserted it after the ordinary specific character.

In those cases in which a genus includes only a single[Pg x]
species, I have followed the practice of some botanists,
and given only the generic character, believing it to be
impossible, before a second species is discovered, to know
which characters will prove of specific, in contradistinction
to generic, value.

In accordance with the Rules of the British Association,
I have faithfully endeavoured to give to each species
the first name attached to it, subsequently to the introduction
of the binomial system, in 1758, in the tenth
edition[1] of the ‘Systema Naturæ.’ In accordance with
the Rules, I have rejected all names before this date,
and all MS. names. In one single instance, for reasons
fully assigned in the proper place, I have broken through
the great law of priority. I have given much fewer
synonyms than is usual in conchological works; this
partly arises from my conviction that giving references
to works, in which there is not any original matter, or
in which the Plates are not of a high order of excellence,
is absolutely injurious to the progress of natural history,
and partly, from the impossibility of feeling certain to
which species the short descriptions given in most works
are applicable;—thus, to take the commonest species, the
Lepas anatifera, I have not found a single description
(with the exception of the anatomical description by
M. Martin St. Ange) by which this species can be
certainly discriminated from the almost equally common
Lepas Hillii. I have, however, been fortunate in having[Pg xi]
been permitted to examine a considerable number of authentically
named specimens, (to which I have attached the
sign (!) used by botanists,) so that several of my synonyms
are certainly correct.

The Lepadidæ, or pedunculated Cirripedes, have been
neglected under a systematic point of view, to a degree
which I cannot quite understand: no doubt they are
subject to considerable variation, and as long as the
internal surfaces of the valves and all the organs of the
animal’s body, are passed over as unimportant, there
will occasionally be some difficulty in the identification
of the several forms, and still more in settling the
limits of the variability of the species. But I suspect
the pedunculated Cirripedes have, in fact, been neglected
owing to their close affinity, and the consequent necessity
of their being included in the same Work with the
Sessile Cirripedes; for these latter will ever present,
I am fully convinced, insuperable difficulties in their
identification by external characters alone.

I will here only further remark, that in the Introduction
I have given my reasons for assigning distinct names to
the several Valves, and to some parts of the included
animal’s body; and that in the Introductory Remarks,
under the general description of the Lepadidæ, I have
given an abstract of my Anatomical Observations.[Pg xii]

CORRIGENDA AND ADDENDA.

Page

[Pg 1]

MONOGRAPH

ON

THE CIRRIPEDIA.

INTRODUCTION.

I should have been enabled to have made this Volume
more complete, had I deferred its publication until I had
finished my examination of all the other known Cirripedes;
but my work would thus have been rendered
inconveniently large. Until this examination is completed,
it will be more prudent not to discuss, in detail,
the position of the Lepadidæ amongst the Cirripedia, or
of these latter in the great class of Crustacea, to which
they now, by almost universal consent, have been
assigned. I may, however, remark that I believe the
Cirripedia do not approach, by a single character, any
animal beyond the confines of the Crustacea: where such
an approach has been imagined, it has been founded on
erroneous observations; for instance, the closed tube
within the stomach, described by M. Martin St. Ange
(to whose excellent paper I am greatly indebted), as
indicating an affinity to the Annelides, is, I am convinced,
nothing but a strong epithelial lining, which I have
often seen ejected with the excrement. Again, a most
distinguished author has stated that the Cirripedia differ
from the Crustacea:—1st. In having “a calcareous shell
and true mantle;” but there is no essential difference, as[Pg 2]
shown by Burmeister, in the shells in these two classes;
and Cirripedes certainly have no more claim to a mantle
than have the bivalve entomostraca. 2d. “In the sexes
joined in one individual;” but this, as we shall see, is not
constant, nor of very much weight, even if constant. 3d.
“In the body not being ringed;” but if the outer integument
of the thorax of any Cirripede be well cleaned, it will
be seen, (as was long ago shown by Martin St. Ange), to
be most distinctly articulated. 4th. “In having salivary
glands;” but these glands are, in truth, the ovaria. 5th.
“In the liver being formed on the molluscous type;” I do
not think this is the case, but I do not quite understand
the point in question. 6th. “In not having a head or
organs of sense;” this is singularly erroneous: Professor
Leidy has shown the existence of eyes in the mature
Cirripede; the antennæ, though preserved, certainly
become functionless soon after the last metamorphosis;
but there exist other organs of sense, which I believe
serve for smelling and hearing: and lastly, so far from
there being no head, the whole of the Cirripede externally
visible, consists exclusively of the three anterior segments
of the head.

The sub-class, Cirripedia, can be divided into three
Orders; the first of which, mainly characterised by having
six pair of thoracic cirri, includes all common Cirripedes:
these latter may be divided into three families,—the
Lepadidæ, or pedunculated Cirripedes, the subject of the
present memoir; the Verrucidæ containing the single
genus Verruca or Clisia; and, lastly, the Balanidæ, which
consist of two very distinct sub-families, the Balaninæ and
Chthamalinæ. Of the other two Orders above alluded
to, one will, I believe, contain the remarkable burrowing
genus Alcippe, lately described by Mr. Hancock, and a
second burrowing genus, or rather family, obtained by
me on the coast of South America. The third Order
is highly singular, and differs as much from all other
Cirripedes as does a Lernæa from other crustaceans; it
has a suctorial mouth, but is destitute of an anus; it has[Pg 3]
not any limbs, and is as plainly articulated as the larva
of a fly; it is entirely naked, without valves, carapace, or
capitulum, and is attached to the Cirripede, in the sack
of which it is parasitic, by two distinct threads, terminating
in the usual larval, prehensile antennæ. I intend to call
this Cirripede, Proteolepas. I mention it here for the sake
of calling attention to any parasite at all answering to
this description.

NOMENCLATURE OF THE VALVES.

Figure I.
CAPITULUM.

Figure II.
SCUTUM of LEPAS.

Figure III.
TERGUM of LEPAS.

Although the present volume is strictly systematic, I
will, under the general description of the Lepadidæ, give
a very brief abstract of some of the most interesting
points in their internal anatomy, and in the metamorphoses
of the whole class, which I hope hereafter to treat,
with the necessary illustrations, in detail. I enter on the
subject of the metamorphoses the more readily, as by this
means alone can the homologies of the different parts be
clearly understood.

On the Names given to the different parts of Cirripedes.

I have unwillingly found it indispensable to give
names to several valves, and to some few of the softer
parts of Cirripedes. The accompanying figure of an
imaginary Scalpellum includes every valve; the two most
important valves of Lepas are also given, in which the
direction of the lines of growth and general shape differ
from those of Scalpellum as much as they do in any genus.
The names which I have imposed will, I hope, be thus
acquired without much difficulty.

Whoever will refer to the published descriptions of
recent and fossil Cirripedia, will find the utmost confusion
in the existing nomenclature: thus, the valve named in the
woodcut the Scutum, has been designated by various well-known
naturalists as the “ventral,” the “anterior,” the
“inferior,” the “ante-lateral,” and the “latero-inferior”
valve; the first two of these titles have, moreover, been
applied to the rostrum or rostral valve of sessile Cirripedes.[Pg 4]
The Tergum has been called the “dorsal,” the “posterior,”
the “superior,” the “central,” the “terminal,”
the “postero-lateral,” and the “latero-superior” valve.
The Carina has received the first two of these identical
epithets, viz. the “dorsal” and the “posterior;” and
likewise has been called the “keel-valve.” The confusion,
however, becomes far worse, when any individual
valve is described, for the very same margin which is
anterior or inferior in the eyes of one author, is the
posterior or superior in those of another; it has often
happened to me that I have been quite unable even to
conjecture to which margin or part of a valve an author
was referring. Moreover, the length of these double
titles is inconvenient. Hence, as I have to describe all
the recent and fossil species, I trust I may be thought
justified in giving short names to each of the more important
valves, these being common to the pedunculated
and sessile Cirripedes.

The part supported by the peduncle, and which is
generally, though not always, protected by valves, I have
designated the Capitulum.

The title of Peduncle, which is either naked or squamiferous,
requires no explanation; the scales on it, and
the lower valves of the capitulum, are arranged in whorls,
which, in the Latin specific descriptions, I have called by
the botanical term of verticillus.

I have applied the term Scutum to the most important
and persistent of the valves, and which can generally be
recognised by the hollow giving attachment to the
adductor scutorum muscle, from the resemblance which
the two valves taken together bear to a shield, and from
their office of protecting the front side of the body.
From the protection afforded by the two Terga to the
dorso-lateral surface of the animal, these valves have
been thus called. The term Carina[2] is a mere translation[Pg 5]
of the name already used by some authors, of Keel-Valve.

The Rostrum has been so called from its relative
position to the carina or keel. There is often a Sub-carina
and a Sub-rostrum.

The remaining valves, when present, have been called
Latera; there is always one large upper one inserted
between the lower halves of the scuta and terga, and this
I have named the Upper Latus or Latera; the other
latera in Pollicipes are numerous, and require no special
names; in Scalpellum, where there are at most only three
pair beneath the Upper Latera, it is convenient to speak
of them (vide Woodcut, I,) as the Carinal, Infra-median,
and Rostral Latera.

As each valve often requires (especially amongst the
fossil species) a distinct description, I have found it indispensable
to give names to each margin. These have
mostly been taken from the name of the adjoining valve,
(see fig. I.) In Lepas, Pollicipes, &c., the margin of the
scutum adjoining the tergum and upper latus, is not divided
(fig. II) into two distinct lines, as it is in Scalpellum,
and is therefore called the Tergo-lateral margin. In
Scalpellum (fig. I) these two margins are separately
named Tergal and Lateral. The angle formed by the
meeting of the basal and lateral or tergo-lateral margins,
I call the Baso-lateral angle; that formed by the basal
and occludent margins, I call, from its closeness to the
Rostrum, the Rostral angle. In Pollicipes the carinal
margin of the tergum can be divided into an upper and
lower carinal margin; of this there is only a trace (fig. I)
in Scalpellum.

That margin in the scuta and terga which opens and
shuts for the exsertion and retraction of the cirri, I have
called the Occludent margin. In the terga of Lepas
(fig. III) and some other genera, the occludent margin
is highly protuberant and arched, or even formed of two
distinct sides.

Occasionally, I have referred to what I have called the[Pg 6]
primordial valves: these are not calcified; they are formed
at the first exuviation, when the larval integuments are
shed: in mature Cirripedes they are always seated, when
not worn away, on the umbones of the valves.

The membrane connecting the valves, and forming the
peduncle, and sometimes in a harder condition replacing
the valves, I have often found it convenient to designate
by its proper chemical name of Chitine, instead of by
horny, or other such equivalents. When this membrane
at any articulation sends in rigid projections or crests, for
the attachment of muscles or any other purpose, I call
them, after Audouin, apodemes. For the underlying true
skin, I use the term corium.

The animal’s body is included within the capitulum,
within what I call the sack (see Pl. IV, figs. 2 and 8´ a, and
Pl. IX, fig. 4). The body consists of the thorax supporting
the cirri, and of an especial enlargement, or downward
prolongation of the thorax, which includes the stomach,
and which I have called the prosoma. (Pl. IX, fig. 4 n).
The cirri are composed of two arms or rami, supported
on a common segment or support, which I call the pedicel.
The caudal appendages are two little projections, either
uni-or multi-articulate (Pl. IV, fig. 8´ a), on each side of
the anus, and just above the long proboscis-like penis.
On the thorax and prosoma, or on the pedicels of the
cirri, there are in several genera, long, thin, tapering
filaments, which have generally been supposed to serve
as branchiæ; these I call simply filaments, or filamentary
appendages (Pl. IX, fig. 4 g-l). The mouth (fig. 4 b) is
prominent, and consists of palpi soldered to the labrum;
mandibles, maxillæ, and outer maxillæ, these latter serve
as an under lip; to these several organs I sometimes
apply the title used by Entomologists, of “trophi.”
Beneath the outer maxillæ, there are either two simple
orifices or tubular projections; these, I believe, serve as
organs of smell, and have hence called them the olfactory
orifices. Within the sack, there are often two sheets of
ova (Pl. IV, fig. 2 b), these I call (after Steenstrup, and[Pg 7]
other authors) the ovigerous Lamellæ; they are united to
two little folds of skin (Pl. IV, fig. 2 f), which I call the
ovigerous Fræna.

From the peculiar curved position which the animal’s
body occupies within the capitulum, I have found it far
more convenient (not to mention the confusion of nomenclature
already existing) to apply the term Rostral instead
of ventral, and Carinal instead of dorsal, to almost
all the external and internal parts of the animal. Cirripedes
have generally been figured with their surfaces of
attachment downwards, hence I speak of the lower or
Basal margins and angles, and of those pointing in an
opposite direction as the Upper; strictly speaking, as we
shall presently see, the exact centre of the usually broad
and flat surface of attachment is the anterior end of the
animal, and the upper tips of the Terga, the posterior
end of that part of the animal which is externally visible;
but in some cases, for instance in Coronula, where the
base is deeply concave, and where the width of the shell
far exceeds the depth, it seemed almost ridiculous to call
this, the anterior extremity; as likewise does it in
Balanus to call the united tips of the Terga, lying deeply
within the shell, the most posterior point of the animal,
as seen externally.

I have followed the example of Botanists, and added
the interjection [!] to synonyms, when I have seen an
authentic specimen bearing the name in question.

Every locality, under each species, is given from specimens
ticketed in a manner and under circumstances
appearing to me worthy of full confidence,—the specific
determination being in each case made by myself.[Pg 8]

Class—CRUSTACEA. Sub-Class—CIRRIPEDIA.

Family—LEPADIDÆ.

Cirripedia pedunculo flexili, musculis instructo: scutis[3]
musculo adductore solummodô instructis: valvis cæteris,
siquæ adsunt, in annulum immobilem haud conjunctis.

Cirripedia having a peduncle, flexible, and provided
with muscles. Scuta[3] furnished only with an adductor
muscle: other valves, when present, not united into an
immovable ring.

Metamorphoses.—I will here briefly describe the Metamorphoses,
as far as known, common to all Cirripedia,
but more especially in relation to the present family.
I may premise, that since Vaughan Thompson’s capital
discovery of the larvæ in the last stage of development in
Balanus, much has been done on this subject: this same
author subsequently published[4] in the ‘Philosophical
Transactions,’ an account of the larvæ of Lepas and
Conchoderma (Cineras) in the first stage; and seeing how
totally distinct they were from the larva of the latter stage
in Balanus, he erroneously attributed the difference to[Pg 9]
the difference in the two families, instead of to the stage
of development. Burmeister[5] first showed, and the discovery
is an important one, that in Lepas the larvæ pass
through two totally different stages. This has subsequently
been proved by implication to be the case in
Balanus, by Goodsir,[6] who has given excellent drawings
of the larva in the first stage; and quite lately,
Mr. C. Spence Bate, of Swansea, has made other detailed
observations and drawings of the larvæ of five species
in this same early stage, and has most kindly permitted
me to quote from his unpublished paper[7]. I am enabled
to confirm and generalise these observations, in all the
Cirripedes in the Order containing the Balanidæ and
Lepadidæ.

The ova, and consequently the larvæ of the Lepadidæ,
in the First Stage, whilst within the sack of the parent,
vary in length from .007 to .009 in Lepas, to .023 of an
inch in Scalpellum: my chief examination of these larvæ
has been confined to those of Scalpellum vulgare; but I
saw them in all the other genera. The larva is somewhat
depressed, but nearly globular; the carapace anteriorly is
truncated, with lateral horns; the sternal surface is flat
and broad, and formed of thinner membrane than the
dorsal. The horns just alluded to are long in Lepas
and short in Scalpellum; their ends are either rounded
and excessively transparent, or, as in Ibla, furnished with
an abrupt, minute, sharp point: within these horns, I
distinctly saw a long filiformed organ, bearing excessively
fine hairs in lines, so exactly like the long plumose spines
on the prehensile antennæ of the larvæ in the last stage;
that I have not the least doubt, that these horns are the
cases in which antennæ are in process of formation. Posteriorly[Pg 10]
to them, on the sternal surface, near each other,
there are two other minute, doubly curved, pointed
horns, about .004 in length, directed posteriorly; and
within these I again saw a most delicate articulated filiformed
organ on a thicker pedicel: in an excellent drawing,
by Mr. C. S. Bate, of the larva of a Chthamalus
(Balanus punctatus of British authors), after having
kept alive and moulted once, these organs are distinctly
shown as articulated antennæ (without a case),
directed forwards: hence, before the first moult in Scalpellum,
we have two pair of antennæ in process of formation.
Anteriorly to the bases of these smaller antennæ
is seated the heart-shaped eye, (as I believe it to be,)
.001 in diameter, with apparently a single lens, surrounded,
except at the apex, by dark-reddish pigment-cells.
In some cases, as in some species of Lepas, the
larvæ, when first excluded from the egg, have not an eye,
or a very imperfect one.

There are three pairs of limbs, seated close together
in a longitudinal line, but some way apart in a transverse
direction: the first pair always consists of a single
spinose ramus, it is not articulated in Scalpellum, but is
multi-articulate in some genera; it is directed forwards.
The other two pair have each two rami, supported on
a common haunch or pedicel: in both pair, the longer
ramus is multi-articulate, and the shorter ramus is without
articulations, or with only traces of them: the longer
spines borne on these limbs (at least, in Scalpellum and
Chthamalus,) are finely plumose. The abdomen terminates,
a little beyond the posterior end of the carapace, in a
slightly upturned horny point; a short distance anteriorly
to this point, a strong, spinose, forked projection depends
from the abdominal surface.

Messrs. V. Thompson, Goodsir, and Bate, have kept
alive for several days the larvæ of Lepas, Conchoderma,
Balanus, Verruca, and Chthamalus, and have described
the changes which supervene between the first and third
exuviations. The most conspicuous new character is the[Pg 11]
great elongation of the posterior point of the carapace
into an almost filiform, spinose point in Lepas, Conchoderma,
Chthamalus, and Balanus, but not according to
Goodsir, in one of the species of the latter genus. The
posterior point, also, of the abdomen becomes developed
in Balanus (Goodsir) into two very long, spear-like processes,
serrated on their outer sides; in Lepas and Conchoderma,
according to Thompson, into a single, tapering
spinose projection; and in Chthamalus, as figured by Mr.
Bate, the posterior bifid point, as well as the depending
ventral fork, increase much in size. Another important
change, which has been particularly attended to by Mr.
Bate, is the appearance of spinose projections and spines
(some of which are thick, curved, and strongly plumose,
or, almost pectinated along their inner sides) on the
pedicels and lower segments of the shorter rami of the
two posterior pairs of limbs.

The mouth in its earliest condition alone remains to
be described; in S. vulgare, it is seated on a very slight
prominence, in a most remarkable situation, namely, in a
central point between the bases of the three pairs of legs.
I traced by dissection the œsophagus for some little way,
until lost in the cellular and oily matter filling the whole
animal, and it was directed anteriorly, which is the
direction that might have been expected, from the course
followed by the œsophagus in the larva in the last stage,
and in mature Cirripedes. Mr. A. Hancock has called
my attention to a probosciformed projection on the under
side of the larva of Lepas fascicularis, when just escaped
from the egg. Mr. Bate has described this same proboscis
in Balanus and Chthamalus, and states the important
fact, that it is capable of being moved by the
animal; and, lastly, I have seen it in an Australian Chthamalus,
and in Ibla, of remarkable size. This proboscis,
which is always directed posteriorly, (like the mouth in
the mature animal,) certainly answers to the mouth as
made out by dissection in Scalpellum; and I believe I
saw, as has Mr. Bate, a terminal orifice: it certainly does[Pg 12]
not possess any trophi. In Ibla (in which the larva is
large enough for dissection), the base of the proboscis
arises posteriorly to the first pair of legs, and the orifice
at the other end reaches beyond or posteriorly to the
point, where the mouth in Scalpellum opens, namely between
the middle pair of legs. The mouth being either
so largely probosciformed or seated only on a slight
eminence, in two genera so closely allied as Ibla and
Scalpellum, and (judging from Mr. Thompson’s figures,
and from what I have seen myself,) in the species of the
same genus Lepas, is a singular difference: in the cases in
which, at first, the proboscis is absent, it would probably
soon be developed. I cannot but suppose that the inwardly
directed spines on the bases of the two posterior
legs, which are so rapidly developed, serve some important
end, namely, as organs of prehension for the larvæ, like the
mandibles and maxillæ of mature Cirripedes, for seizing
their prey, and conveying it to their moveable mouths,
conveniently seated for this purpose.

The first pair of legs answers, as I believe from reasons
hereafter to be assigned, to the outer pair of maxillipods
in the higher crustacea; and the other four legs to the
first two pair of thoracic limbs in these same crustacea;
this being the case, the highly remarkable position of the
mouth in the larva, either between the bases of the two
posterior pair of legs, or at least posteriorly to the first
pair, together with the probable functions of the spiny
points springing from the basal segments of the two
hinder pair of true thoracic limbs, forcibly bring to mind
the anomalous structure of the mouth being situated in
the middle of the under side of the thorax, in Limulus,—that
most ancient of crustaceans, and therefore one
likely to exhibit a structure now embryonic in other orders.
I will only further remark, that I suspect that the truncation
of the anterior end of the carapace, has been
effected by the segments having been driven inwards,
and consequently, that the larger antennæ within the
lateral horns, though standing more in front than the[Pg 13]
little approximate pair, are normally the posterior of the
two pair. According to Milne Edwards, the posterior
pair are normally seated outside the anterior pair, and this
is the case with those within the lateral horns.

Larva in the Second Stage.—Notwithstanding the
considerable changes, already briefly given, which the
larva undergoes during the first two or three exuviations
after leaving the egg, all these forms may be conveniently
classed under the first stage. The larva in the
Second stage is known only from a single specimen
described, figured, and found by Burmeister,[8] adhering to
sea-weed in the midst of other larvæ of Lepas in the
last stage. In its general shape and compressed form,
it seems to come nearer to the last than to the first stage.
It has only three pair of legs, situated much more posteriorly
on the body than in the first stage, and all directed
posteriorly; they are much shorter than heretofore, and
resemble rather closely those of the last stage, with the
important exception that the first pair has only one ramus.
It is this circumstance which leaves no doubt on my mind,
that we here have the three pair of limbs, of the first
stage, metamorphosed. The body is prolonged some way
behind these limbs, and ends in a blunt, rounded point, in
which, probably, are developed the three posterior pair
of legs and the abdomen of the larva in the last stage.
The mouth is now seated some way anteriorly to the
limbs, is large and probosciformed, and is, I presume, still
destitute of trophi. There are now two closely approximate
eyes, but as yet both are simple. The smaller pair of
antennæ has disappeared. The whole animal was attached
to the sea-weed by a (I presume, pair of,) “fleischigen
Fortsatz,” which Burmeister considers as the prehensile
antennæ, to be presently described, in an early state of
development. I have little doubt that this is correct, for
in an abnormal Cirripede of another order, in which
the larva appears in the first stage with prehensile antennæ,
the eggs have two great projecting horns including[Pg 14]
these organs, and attached by their tips, through some
unknown means, to the sack of the parent, apparently in
the same manner as Burmeister’s larva was attached to
the sea-weed. I will only further remark on the larva
of this Second stage, that its chief development since the
first stage, has been towards its anterior end. The next
great development, to be immediately described, is towards
the posterior end of the animal.

Larva, Last Stage.—My chief examination has been
directed, at this stage of development, to the larvæ of
Lepas australis, which are of unusual size, namely, from
.065 to even almost .1 of an inch in length; I examined,
however, the larvæ of several other species of Lepas, of
Ibla and of Balanus, with less care, but sufficiently to
show that in all essential points of organisation they were
identical; this, indeed, might have been inferred from
the similarity of the larval prehensile antennæ, preserved
in the bases of all mature Cirripedes, and which I have
carefully inspected in almost every genus. The larvæ in
this final stage, in most of the genera, have increased many
times in size since their exclusion from the egg; for
instance, in Lepas australis, from .007 to .065, or even to
.1 of an inch. They are now much compressed, nearly
of the shape of a cypris or mussel-shell, with the anterior
end the thickest, the sternal surface nearly or quite
straight, and the dorsal arched. Almost the whole of
what is externally visible consists of the carapace; for
the thorax and limbs are hidden and enclosed by its
backward prolongation; and even at the anterior end of
the animal, the narrow sternal surface can be drawn up,
so as to be likewise enclosed. As in several Stomapod
crustaceans, the part of the head bearing the antennæ
and organs of sense, in front of the mouth, equals, or
even exceeds in length, and more than exceeds in bulk,
the posterior part of the body, consisting of the enclosed
thorax and abdomen. I will now briefly describe, in the
following order, the carapace, the organs of sense, mouth,
thorax and limbs, abdomen, and internal viscera.[Pg 15]

The form of the Carapace has been sufficiently described;
it consists of thick chitine membrane, marked with
lines, and sometimes with stars and other patterns; it is
obscurely divided into two halves by a line or suture along
part of the dorsal margin; these halves or two valves are
drawn together by an adductor muscle, in the same relative
position as in the mature Cirripede. The part overhanging
and enclosing the thorax is lined by an excessively
delicate membrane, obviously homologous with the lining
of the sack in the mature animal, and is nothing but a
duplicature of the carapace, rendered very thin from being
on the under or protected side: a layer of true skin or
corium, probably double, separates these two folds.

Acoustic Organs.—On the borders of the carapace, at
the anterior end, on the sternal surface, there are two
minute orifices, in L. australis .002 in diameter, sometimes
having a distinct border round them; the membrane
of the carapace on the inside is prolonged upwards
and inwards in two short funnel-shaped tubes, lodged
in closed sacks of the corium: within these sacks on each
side a delicate bag is suspended, and hangs in the mouth
of the above funnel; at the upper end a large nerve could
be distinctly seen to enter the bag: I cannot doubt that
this is a sense-organ; from its position and from the animal
not feeding (as we shall presently see), I conclude that
it is an acoustic organ.

Antennæ.—These are large and conspicuous; they are
attached very obliquely on the sternal surface, a little way
from the anterior end of the carapace, beyond which,
when exserted, they extend;[9] they can (at least in Ibla)[Pg 16]
be retracted within the carapace. They consist of three
segments: the first or basal one is much larger than the
others, and apparently always has a single spine on the
outer distal margin. The second segment consists either
of a large, thin, circular, sucking disc, or is hoof-like
(Tab. V, figs. 5, 10, 11, 12); in all cases it is furnished
with one or more spines, (seven very long ones in Lepas,) on
the exterior-hinder margin. The third and ultimate segment
is small; it is articulated on the upper surface of the
disc, and is directed rectangularly outwards; it is sometimes
notched, and even shows traces of being bifid; it
bears about seven spines at the end; some of these spines
are hooked, others simple, and in Lepas and Conchoderma,
two or three are very long, highly flexible, and plumose,
a double row of excessively fine hairs being articulated on
them. I can hardly doubt that these latter spines, (within
which the purple corium could be seen to enter a little
way,) floating laterally outwards, serve as feelers. The
antennæ, at first, are well furnished with muscles. They
serve, in Lepas, according to Mr. King, and in Balanus,
according to Mr. Bate, and as I saw myself in another
unnamed order, for the purpose of walking, one limb being
stretched out before the other; but their main function
is to attach the larva for its final metamorphosis into a
Cirripede. The disc can adhere even to so smooth a
surface as a glass tumbler.[10] The attachment is at first
manifestly voluntary, but soon becomes involuntary and
permanent, being effected by special and most remarkable
means, which will be most conveniently described in a
later part of this Introduction. I will here only state
that I traced with ease the two cement-ducts running
from two large glandular bodies, to within the antennæ
up to the discs.

Eyes.—Close behind the basal articulations of the
antennæ, the sternal surface consists of two approximate,
elongated, narrow, flat pieces, or segments. These[Pg 17]
Burmeister considers as the basal segments of the antennæ:
as they are not cylindrical, I do not see the
grounds for this conclusion: their posterior ends are
rounded, and the membrane forming them is reflected
inwards, in the form of two, forked, horny apodemes,
together resembling two letters, UU, close together; these
project up, inside the animal, for at least one third of its
thickness from the sternal to the dorsal surface. The
two great, almost spherical eyes in L. australis, each 1/150th
of an inch in diameter, are attached to the outer arms,
thus, °UU°, in the position of the two full stops. Hence
the eyes are included within the carapace. Each eye consists
of eight or ten lenses, varying in diameter in the
same individual from 1/2000 to 3/2000th of an inch, enclosed in
a common membranous bag or cornea, and thus attached
to the outer apodemes. The lenses are surrounded half
way up by a layer of dark pigment-cells. The nerve does
not enter the bluntly-pointed basal end of the common
eye, but on one side of the apodeme. The structure here
described is exactly that found, according to Milne
Edwards, in certain crustacea. In specimens just
attached, in which no absorption has taken place,
two long muscles with transverse striæ may be found
attached to the knobbed tips of the two middle arms
of the two °UU°, and running up to the antero-dorsal
surface of the carapace, where they are attached; other
muscles (without transverse striæ) are attached round
the bases, on both sides of both forks. The action of
these muscles would inevitably move the eyes, but I
suspect that their function may be to draw up the narrow,
deeply folded, sternal surface, and thus cause the retraction
of the great prehensile antennæ within the carapace.

Mouth.—This is seated in exactly the same position
as in the mature Cirripede, on a slight prominence,
fronting the thoracic limbs, and so far within the carapace,
that it was obviously quite unfitted for the seizure
of prey; and it was equally obvious, that the limbs were
natatory, and incapable of carrying food to the mouth.[Pg 18]
This enigma was at once explained by an examination of
the mouth, which was found to be in a rudimentary condition
and absolutely closed, so that there would be
no use in prey being seized. Underneath this slightly
prominent and closed mouth, I found all the masticatory
organs of a Cirripede, in an immature condition. The
state of the mouth will be at once understood, if we
suppose very fluid matter to be poured over the protuberant
mouth of a Cirripede, so as to run a little way
down, in the shape of internal crests, between the different
parts, and in the shape of a short, shrivelled,
certainly closed tube, a little way (.008 of an inch in
L. australis) down the œsophagus. Hence, the larva in
this, its last stage, cannot eat; it may be called a
locomotive Pupa;[11] its whole organisation is apparently
adapted for the one great end of finding a proper site for
its attachment and final metamorphosis.

Thorax and Limbs.—The thorax is much compressed,
and consists of six segments, corresponding with the six
pair of natatory legs; the anterior segments are much
plainer (even the first being distinctly separated by a fold
from the mouth), than the posterior segments, which is
exactly the reverse of what takes place in the mature
Cirripede; in the latter, the first segment is confounded
with the part bearing the mouth. The epimeral elements
of the thorax are distinguishable; the sternal surface is
very narrow, and is covered with complicated folds and
ridges. The six pair of legs are all close, one behind the
other, and all are alike in having a haunch or pedicel of
two segments, directed forwards, bearing two arms or
rami, each composed of two segments, the outer ramus[Pg 19]
being a little longer than the inner one. On the lower
segments in both rami of all the limbs, there is a single
spine. In all the limbs, the obliquely truncated summit
of the terminal segment of the inner ramus bears three
very long, beautifully plumose spines: in the first pair,
the summit of the outer ramus bears four, and in the
five succeeding pair, six similar spines. This difference,
small as it is, is interesting, as recalling the much greater
difference between the first and succeeding pairs, in the
first and second stage of development. The terminal segments
of all the rami, bearing the long plumose spines,
are directed backwards. The limbs and thorax are well
furnished with striated muscles. The animal, according
to Mr. King, swims with great rapidity, back downwards.
The limbs can be withdrawn within the carapace.

Abdomen and Caudal Appendages.—The abdomen is
small, and its structure might easily be overlooked without
careful dissection of the different parts: it consists of
three segments; the first can be seen to be distinct from
the last thoracic segment, bearing the sixth pair of limbs,
only from the fold of the epimeral element, and from its
difference in shape; the second segment is very short,
but quite distinct; the third is four or five times as long
as the second, and bears at the end two little appendages,
each consisting of two segments, the lower one with a
single spine, and the upper one with three, very long,
plumose spines, like those on the rami of the thoracic
limbs. The abdomen contains only the rectum and two
delicate muscles running into the two appendages, between
the bases of which the anus is seated.

Internal Viscera.—Within the body, in front of the
mouth, it was easy to find the stomach (with two pear-shaped
cæca at the upper end), running first anteriorly,
and then curving back and reaching the anus by a long
rectum, difficult to be followed: it appeared, however,
to me, that this stomach had more relation to the young
Cirripede, of which every part could now generally be
traced, than to the larva, with its closed and rudimentary[Pg 20]
mouth: the fact, however, of its being prolonged to the
anus, which is in a different position in the larva and
mature state, shows that the stomach serves, at least, as
an excretory channel. Besides the stomach, the several
muscles already alluded to, and much pulpy and oily
matter, the only other internal organs consist of two long,
rather thick, gut-formed masses, into the anterior ends
of which the cement-ducts running from the prehensile
antennæ could be traced. These masses are formed
of irregular orange balls, about .001 of an inch in
diameter, made up of rather large cells, so to have a
grape-like appearance, held together by a transparent
pale yellowish substance, but apparently not enclosed in
a membrane: these masses lie rather obliquely, and approach
each other at their anterior ends; they extend
from above the compound eyes, to the cæca of the stomach
to which they cohere, but in young specimens, they extend
some way beyond the cæca, between the folds of the
carapace. The two cement-ducts, at the points where
they enter these bodies, expand and are lost; at this point,
also, the little orange-coloured masses of cells have the
appearance of being broken down into a finer substance.
Within the cement-ducts I saw a distinct chord of rather
opaque cellular matter. We shall presently see, that these
gut-formed masses are the incipient ovaria.

The Young Cirripede within the Larva.—Several times
I succeeded in dissecting off the integuments of the
lately-attached larva, and in displaying the young Lepas
australis entire. The following description applies to the
Cirripede in this state; but for convenience sake, I shall
occasionally refer to its condition when a little more
advanced. I may premise, and the fact in itself is curious,
that the bivalve-like shell of the larva, together with the
compound eyes, is first moulted, and some time afterwards,
the inner lining of the sack, together with the integuments
of the thorax and of the natatory legs: hence, I
often found specimens, which externally seemed to have
perfected their metamorphoses, but which, within their[Pg 21]
sacks, retained all the characters of the natatory larva.
According to Mr. King, the larva of Lepas throws off its
external shell five days after becoming attached. Whilst
the young Lepas is closely packed within the larva, the
capitulum, as known by the five valves, about equals in
length the peduncle. The peduncle occupies the anterior
half of the larva; when fully stretched, it becomes narrower
and slightly longer than the capitulum; the separation
between the capitulum and peduncle is almost
arbitrary in the mature animal, and corresponds with no
particular line in the larva. Even at this early period,
the muscles of the peduncle are quite distinct. No
vestige is preserved in the outer integument, of the sternal
and dorsal sutures of the larval carapace; but in the
corium of the peduncle, three coloured marks which
occur near the eyes, and two little curled marks which
occur near the acoustic orifices of the larva, are all preserved
for some time after maturity. The compound
eyes, as we have seen, are attached to apodemes, springing
from the sternal surface of the larval carapace, and
are consequently cast off with it: whilst the young Cirripede
is packed within the larva, the outer integument of
its peduncle necessarily forms a deep transverse fold passing
over the eyes and apodemes, and this, as we shall
presently see, plays an important part in the future
position of the animal. The antennæ are not moulted
with the carapace, but left cemented to the surface of attachment;
their muscles are converted into sinewy fibres,
the corium after a short period is absorbed, and they are
then preserved in a functionless condition. No trace of
the two acoustic sacks can be perceived in the corium
of the young Cirripede, excepting the coloured marks
above alluded to.

In the young capitulum, the five valves stand some
way apart from each other; they are elegant objects
under the microscope; they are not calcified, but consist
exclusively of chitine; they are rather thick, composed
of an outer membrane lined by hexagonal prisms,[Pg 22]
quite unlike any other membrane in the animal. These
valves, which I have called primordial valves, resemble
pretty closely in shape the valves of the mature animal;
the fork of the carina, however, is indicated only by a
slight constriction above the lower end. After the
exuviation of the larval integuments, and when calcification
commences, the first layer of shell is deposited
under, and then round these primordial valves. The latter,
in well preserved old specimens, may often be detected
on the umbones of the scuta, terga, and carina, but not
on the umbones of any other valves.

The mouth seems one of the earliest parts developed:
in the youngest larva dissected, I could make out at least
points corresponding with each organ; and, at the period
when the young Cirripede could be dissected out of its
larval envelopes, their general details were quite plain.
The labrum, however, had not become bullate. The
mouth, as we have seen, is formed under the rudimentary
mouth of the larva, and at the same relative
spot occupied by the probosciformed mouth of the larva
in the second stage. Thus far, in the young Cirripede
and larva, there has been no great change in the relative
positions of the parts: the rudimentary eyes, however, of
the former are developed posteriorly to (or above, as applied
to a Cirripede,) the cast-off compound eyes of the
larva; but the position of the mouth, of the antennæ, and
of the several coloured marks in the corium, prove to
demonstration, the correspondence in both of part to part.
The case is rather different with what follows.

The Cirri are developed at first of considerable length,
so that the young animal may soon provide itself with
food; in Lepas australis they are of great length, the
sixth pair consisting of seventeen or eighteen obscure
segments. The extreme tips of the twenty-four rami
of the six pair of cirri, are formed within the twenty-four,
corresponding, little, bi-segmental rami of the six
pair of natatory legs; but as the cirri are many times
longer than these legs, they occupy in a bundle the[Pg 23]
whole thorax of the larva; no part whatever of the
thorax of the Cirripede is formed within the thorax
of the larva, but (together with the pedicels of the anterior
cirri) within the cephalic cavity. As a consequence
of this, the longitudinal axis of the thorax of the young
Cirripede lies almost transversely to the longitudinal axis
of the larva; and the Cirripede, from this transverse
position of its thorax, comes to be, as it were, internally,
almost cut in twain, and the sack thus produced. As
soon as the young Cirripede is free and can move itself,
the cirri are curled up, and the thorax is advanced towards
the orifice of the capitulum, its longitudinal axis
resuming the position of approximate parallelism to the
longitudinal axis of the whole body, which it had in the
larval condition. The reader will, perhaps, understand
what I mean, if he will look at the mature Cirripede,
figured in Pl. IX, fig. 4. In this, he will see that the
body or thorax is united to the peduncle only by a small
part below the mouth; on the other hand, if he imagines
the whole bottom of the body (as high up as the letter h)
united and blended into the peduncle, he will see the
state in which these parts exist in the larva. Now, let him
greatly shorten the cirri, so as to resemble the natatory
legs of the larva, and then imagine a young Cirripede,
with cirri of full length, formed within the old one, he
will see that the new thorax supporting the cirri will
have to be developed in an almost transverse position,—the
animal consequently being internally almost separated
into twain.

Of the internal organs, whilst the Cirripede is still
within the larva, I have already mentioned the stomach
with its pair of cæca: from the retracted position of the
thorax and rudimentary abdomen, and consequently of
the anus, compared with these parts in the larva, the
alimentary canal is not above half its former length.
There is, as yet, no trace of the filaments supposed by
some to act as branchiæ, at the base of the first pair
of cirri. Nor could I perceive a trace of the testes or[Pg 24]
vesiculæ seminales: the penis is represented by a minute,
apparently imperforate projection. I have already briefly
described the pair of large, gut-formed bodies in the
larva, into the anterior ends of which the cement-ducts
ran, and evidently derived their slightly opaque, cellular
contents. At a very early age, before the young Cirripede
can be distinctly made out, the posterior ends of these
gut-formed bodies are absorbed, so as not to pass beyond
the cæca of the stomach. When the young Cirripede is
plainly developed within the larva, these bodies in a relatively
reduced condition are still distinct near the cæca,
and at the opposite or anterior end (i. e. lower, in the
position in which Cirripedes are usually figured), they have
branched out into a sheet of delicate inosculating tubes;
these could be traced by every stage, until, in the young
perfected Cirripede, they filled the peduncle as ordinary
ovarian tubes. In the larva, the two gut-formed bodies
or incipient ovaria keep of equal thickness from one to
the other end, but in the mature Cirripede, the ovarian
tubes in the peduncle and the small, glandular, grape-like
masses, near the stomach-cæca, are connected only
by a delicate tube; this I failed in tracing in specimens
in the very immature condition of those now under
description.

The larva fixes itself with its sternal surface parallel
and close to the surface of attachment, and the antennæ
become cemented to it: if the Cirripede, after its
metamorphosis had remained in this position, the cirri
could not have been exserted, or only against the surface
of attachment; but there is a special provision, that
the young Cirripede shall immediately assume its proper
position at right angles to the position which it held
whilst within the larva, namely with its posterior end
upwards. This is effected in a singular manner by the
exuviation of the great compound eyes, which we have
seen are fastened to the outer arms of the double °UU°-like,
sternal apodemes: these together with the eyes
stretch transversely across, and internally far up into,[Pg 25]
the body of the larva; and, as the whole has to be rejected
or moulted, the membrane of the peduncle of the young
Cirripede has necessarily to be formed with a wide and
deep inward fold, extending transversely across it; this
when stretched open, after the exuviation of the larval
carapace and apodemes, necessarily causes the sternal
side of the peduncle to be longer than the dorsal, and,
as a consequence, gives to the young Cirripede its normal
position, at right angles to that of the larva when first
attached.

I may here state, that I have examined the larvæ in
this the final or perfect stage in four species of Lepas, in
Conchodermavirgata, Ibla quadrivalvis, and, though rather
less minutely, in Balanus balanoides, and I find all
essential points of organisation similar. With the exception
of diversities in the proportional sizes of the different
parts, and in the patterns on the carapace, the differences,
even in the arrangement of the spines on the limbs and
antennæ, are less than I should have anticipated.

I have in this abstract treated the metamorphoses at
greater length than I should otherwise have done, on
account of the great importance of arriving at a correct
homological interpretation of the different parts of the
mature animal. In Crustacea, according to the ordinary
view, there are twenty-one segments; of these I can recognise
in the Cirripede, on evidence as good as can
generally be obtained, all with the exception of the four
terminal abdominal segments; these do not occur in any
species known to me, in any stage of its development.
If that part of the larva in front of the mouth, bearing the
eyes, the prehensile antennæ, and in an earlier stage two
pair of antennæ, be formed, as is admitted in all other
Crustacea, of three segments, then beyond a doubt, from
the absolute correspondence of every part, and even every
coloured mark, the peduncle of the Lepadidæ is likewise
thus formed. The peduncle being filled by the branching
ovarian tubes is no objection to this view, for I am[Pg 26]
informed on the high authority of Mr. J. D. Dana,[12]
that this is the case with the cephalo-thorax in some true
Crustaceans, for instance, in Sapphirina. To proceed,
the mouth, formed of mandibles, maxillæ, and outer
maxillæ, correspond with the fourth, fifth, and sixth
segments of the archetype Crustacean. Posteriorly
to the mouth, we come, in the larva, to a rather wide
interspace without any apparent articulation or organ,
and then to the thorax, formed of six segments, bearing
the six pair of limbs, of which the first pair differs slightly
from the others. The thorax is succeeded by three small
segments, differently shaped, with the posterior one alone
bearing appendages; these segments, I cannot doubt,
from their appearance alone, and from their apparent
function of steering the body, are abdominal segments.
If this latter view be correct, the thoracic segments are
the six posterior ones of the normal seven segments, and
there must be two segments missing between the outer
maxillæ and first thoracic pair of legs, which latter on this
view springs from the ninth segment. Now, in a very singular
Cirripede, already alluded to under the name of
Proteolepas, the two missing segments are present, the
mouth being actually succeeded by eight segments, and
these by the three usual abdominal segments,—every
segment in the body being as distinct as in an Annelid:
hence in Proteolepas, adding the three segments for the
mouth and three for the carapace, we have altogether[Pg 27]
seventeen segments, which, as I stated, is the full number
ever observed in any Cirripede, the four missing ones
being abdominal, and, I presume, the four terminal segments.
That the cavity in which the thorax is lodged,
in the larva and therefore in the mature Cirripede, is
simply formed by the backward production of the carapace,
does not require any discussion. The valves have
no homological signification.

As we have just seen that the first pair of natatory legs
is borne on the ninth segment of the body, so it must be
with the first pair of cirri, which consequently correspond
to the outer maxillipods (the two inner pair of maxillipods
or pied-machoires being here aborted) of the higher Crustacea,
and hence their difference from the five posterior
pair, which correspond with the five, ordinary pair of ambulatory
legs in these same Crustacea. The part of the
body, which I have called the prosoma, that is the protuberant,
non-articulated, lower part of the thorax (Pl. IX,
fig. 4 n), is a special development, either of the ninth
segment, bearing the first pair of cirri, or of the segments
corresponding with the organs of the mouth. The three
abdominal segments of the larva are represented in the
mature Cirripede, in the Order containing the Lepadidæ,
only by a minute, triangular gusset, let in between the
V-shaped tergal arches of the last thoracic segment: in
this gusset, small as it is, is seated the anus, and on each
side the caudal appendages, often rudimentary and sometimes
absent. In another order, I may remark, (including,
probably, the Alcippe of Mr. Hancock,) the cirri,
of which there are only three pair, are abdominal.

I feel much confidence, that the homologies here given
are correct. The cause of their having been generally
overlooked arises, I believe, from the peculiar manner,
already described, in which the animal, during its last
metamorphosis, is internally almost intersected: even for
some little time after discovering that the larval antennæ
were always embedded in the centre of the surface of
attachment, I did not perceive, that this was the anterior[Pg 28]
end of the whole animal. The accompanying woodcut
gives at a glance, a view of the homologies of the external
parts: the upper figure (from Milne Edwards) is a
Stomapod Crustacean, Leucifer of Vaughan Thompson,
and the abdomen, which we know becomes in Cirripedes,
after the metamorphosis, rudimentary, and therefore does
not fairly enter into the comparison, is given only in
faint lines: the lower figure is a mature Lepas, with
the antennæ and eyes, which are actually present in the
larva, retained and supposed to have gone on growing.
All that we externally see of a Cirripede, whether pedunculated
or sessile, is the three anterior segments of the
head of a Crustacean, with its anterior end permanently
cemented to a surface of attachment, and with its posterior
end projecting vertically from it.

[m.—Mouth.]

CAPITULUM.

I will now proceed to a general description of the
different parts and organs in the Lepadidæ. The Capitulum
is usually much flattened, but sometimes broadly
oval in section. It is generally formed of five or more
valves, connected together by very narrow or broad strips
of membrane; sometimes the valves are rudimental or
absent, when the whole consists of membrane. When
the valves are numerous, and they occasionally exceed[Pg 29]
a hundred in number, they are arranged in whorls,
with each valve generally so placed as to cover the
interval between the two valves above. Of all the valves,
the scuta are the most persistent; then come the terga,
and then the carina; the rostrum and latera occur only in
Scalpellum and Pollicipes, and in a rudimentary condition
in Lithotrya, and, perhaps, in the fossil genus Loricula.
The valves are formed sometimes of chitine (as in Ibla and
Alepas), but usually of shell, which varies from transparency
to entire opacity. The shell is generally white,
occasionally reddish or purple; exteriorly, the valves are
covered by more or less persistent, generally yellow, strong
membrane. The scuta and terga are always considerably
larger than the other valves: in the different genera
the valves differ so much in shape that little can be predicated
of them in common; even the direction of their
lines of growth differs,—thus, in Lepas and some allied
genera, the chief growth of the scuta and of the carina is
upwards, whereas in Pollicipes and Lithotrya, it is entirely
downwards; in Oxynaspis, and some species of Scalpellum,
it is both upwards and downwards. Even in the
same species, there is often very considerable variation in
the exact shape of the valves, more especially of the
terga. The adductor muscle is always attached to a
point not far from the middle of the scuta, and it generally
has a pit for its attachment. In several genera,
namely, Pæcilasma, Dichelaspis, Conchoderma, and
Alepas, the scuta show a tendency to be bilobed or
trilobed. The valves are placed either at some distance
from each other, or close together; but their growing
margins very rarely overlap each other, though this is
sometimes the case with their upper, free, tile-like apices;
in a few species the scuta and terga are articulated together,
or united by a fold. The membrane connecting
the valves, where they do not touch each other, is like
that forming the peduncle, and is sometimes brilliantly
coloured crimson-red; generally, it appears blueish-gray,
from the corium being seen through. Small pointed[Pg 30]
spines, connected with the underlying corium by tubuli,
are not unfrequently articulated on this membrane: the
tubuli, however, are often present where there are no
spines. To allow of the growth of the capitulum, the
membrane between the valves splits at each period of
exuviation, when a new strip of membrane is formed
beneath, connected on each side with a fresh layer of shell,—the
old and outer slips of membrane disintegrating
and disappearing: when there are many valves, the line of
splitting is singularly complicated. This membrane
consists of chitine,[13] and is composed of numerous fine
laminæ. After the valves have been placed in acid, a
residue, very different in bulk in different genera, is left,
also composed of successive laminæ of chitine. It appears
to me that each single lamina of calcified chitine, composing
the shell, must once have been continuous with a
non-calcified lamina in the membrane connecting the
several valves: at the line where this change in calcification
supervenes, the chitine generally assumes some[Pg 31]
colour, and becomes much harder and more persistent;
and as the whole valve is formed of component laminæ
thus edged (the once continuous laminæ of non-calcified
chitine connecting the valves, having disintegrated and
disappeared) the surfaces of the valves are generally left
covered by a persistent membrane, constituted of these
edgings: this membrane has been called the epidermis.
In some genera, as in Lepas, this so-called epidermis is
seldom preserved, excepting on the last zone of growth:
in Scalpellum and Pollicipes it usually covers the whole
valves. It appears to me that the laminæ of chitine,
and of calcified chitine composing the valves, are both
formed not by secretion, but by the metamorphosis of an
outer layer of corium into these substances.

Within the capitulum is the sack, which, together with
the upper internal part of the peduncle, encloses the
animal’s body. The sack is lined by a most delicate membrane
of chitine, under which there is a double layer of
corium; this double layer is united together by short,
strong, transverse bundles of fibres, branched at both
ends:[14] in some genera, the ovarian tubes extend between
these two layers. We have seen, under the head of the
Metamorphoses, that the delicate tunic lining the sack is
simply a duplicature of the thick membrane and valves
forming the capitulum, the whole being the posterior
portion of the carapace of the larva slightly modified.

Peduncle.—Its length varies greatly in different species,
and even in the same species, according to the situation
occupied by the individual; its lower end is sometimes
pointed, but generally only a little narrower than
the upper end. In outline, the peduncle is usually
flattened, but sometimes quite cylindrical. It is composed
of very strong, generally thick, transparent membrane,
rarely coloured reddish, and often penetrated by
numerous tubuli. The underlying corium is sometimes[Pg 32]
coloured in longitudinal bands. At each period of
growth a new and larger integument is formed under the
old one, which gradually disintegrates and disappears;
the extreme lower point is often deserted by the corium,
and ceases to grow, whilst the whole upper part still
continues increasing in diameter: in length the chief
addition is made (as is clearly seen in those genera having
calcified scales), round the upper margin, at the base of
the capitulum. The surface of the membrane is either
naked or superficially clothed with minute, pointed,
articulated spines, or it is penetrated by calcified scales
or styles, (in Ibla alone formed of chitine,) which pass
through it to the corium, and are added to at their bases,
like the valves, at each period of growth. In Lithotrya
alone the scales of the peduncle are moulted together
with the connecting membrane. These scales on the
peduncle are generally placed symmetrically in whorls,
with each scale corresponding with the junctions of two
scales, both above and below. Except in Scalpellum
ornatum and the fossil Loricula pulchella, they are very
small compared with the valves of the capitulum. When
the scales are symmetrical, new ones are first formed
only round the summit of the peduncle, and only those
in the few uppermost whorls continue to grow or to be
added to at their bases; afterwards membrane is deposited
under them. The shelly matter of the scales
resembles that of the valves, and the manner of growth
is the same; tubuli generally run to and through them
from the corium. From the continued enlargement of
the membrane of the peduncle, the scales come to stand,
in the lower portion, some way apart. In Ibla, new
horny styles are formed indifferently in all parts of the
peduncle. In some species of Pollicipes, the calcareous
styles are not symmetrical or symmetrically arranged;
and besides those first formed round the top of the peduncle,
there are other and larger ones formed near its
base. Lastly, in Lithotrya we have a row of calcareous
discs or an irregular, basal cup, formed in the same[Pg 33]
manner as the valves of the capitulum: in this genus
alone (as already stated,) the calcified scales are moulted,
and here alone their edges are serrated.

The peduncle is lined within by three layers of muscles,
longitudinal, transverse, and oblique, all destitute of the
transverse striæ, characteristic of voluntary muscles; they
run from the bottom of the peduncle to the base of the
capitulum, as in Lepas, or half way up it, as in Conchoderma;
in Alepas alone they surround the whole
capitulum up to its summit. In Lithotrya there are two
little, fan-like, transverse muscles (involuntary), extending
from the basal points of the terga to a central line on the
under side of the carina. The gentle swaying to and
fro movements, and the great power of longitudinal contraction,—movements
apparently common, as I infer
from facts communicated to me by Mr. Peach, to all the
Pedunculata,—are produced by these muscles. The
interior of the peduncle is filled up with a great mass of
branching ovarian tubes; but in Ibla and Lithotrya, the
upper part of the peduncle is occupied by the animal’s
body.

Means of Attachment.—If the peduncle be very carefully
removed (Tab. IX, fig. 7 and Tab. I, fig. 6 b), from
the surface of attachment, quite close to the end, but not
at the actual apex, the larval prehensile antennæ can
always be found: these have been sufficiently described
for our present purpose under the head of the Metamorphoses;
but I may add, that the diagnostic differences
between them in the several genera are briefly given, for
a special purpose, in a discussion on the sexes of Scalpellum
at the end of that genus. We have seen in the
larva, that the cement-ducts, with their opaque cellular
contents, can be traced from within the discs of the
antennæ to the anterior or lower ends of the two gut-formed
bodies, which it can be demonstrated are the
incipient ovaria.

In mature Cirripedes these ducts can be followed, in a
slightly sinuous course, along the muscles on each side[Pg 34]
within the peduncle, till they expand into two small
organs, which I have called cement-glands. These glands
are found with great difficulty, except in Conchoderma
aurita, where they are placed on each side under the inner
layer of corium, at the bottom of the sack, so as to be just
above the top of the peduncle; they resemble in shape a
retort, (Pl. IX, fig. 3.). In Pollicipes mitella and polymerus
they lie half way down the peduncle, close together,
and apparently enclosed within a common membrane; in
these two species the broad end of the gland is bent
towards the neck of the retort. In Scalpellum the position
is the same, but the shape is more globular. In Ibla the
structure is more simple, namely, a tube slightly enlarged,
running downwards, bent a little upwards, and then
resuming its former downward course, the lower portion
forming the duct. The gland contains a strongly coherent,
pulpy, opaque, cellular mass, like that in the
cement-ducts; but in some instances, presently to be
mentioned, this cellular mass becomes converted within
either the ducts or gland, or within both, into transparent,
yellow, tough cement. Generally in Conchoderma, Pollicipes,
and Scalpellum, two ovarian tubes, but in one
specimen of Conchoderma aurita, three tubes, and in Ibla
one tube could be seen running into or forming the
gland; of the nature of the tubes there could not be the
least doubt, for at a little distance from the glands they
gave out branches (Pl. IX, fig. 3), containing ova in every
state of development. In some specimens as in that
figured of Conchoderma aurita, the ovarian tube on one side
of the gland is larger than on the other, and has rather
the appearance of being deeply embedded in the gland
than of forming it; but, in other specimens, the two
ovarian tubes first formed a little pouch, into which their
cellular contents could be clearly seen to enter; and then
this pouch expanded into the gland; thus quite removing
a doubt which I had sometimes felt, whether the ovarian
tube was not simply attached to or embedded in the
gland, without any further connection. By dissection[Pg 35]
the multiple external coats of the gland and ovarian tubes
could be seen to be continuous. The cellular contents of
the tubes passed into the more opaque cellular contents of
the gland, by a layer of transparent, pulpy, pale, yellowish
substance. There appeared in several instances to be a
relation, between the state of fulness and condition of the
contents of the gland, and of the immediately adjoining
portions of the ovarian tubes. In one specimen of
Pollicipes mitella it was clear that the altered, tough,
yellow, transparent, non-cellular contents of the two
glands and ducts, had actually invaded for some little
distance, the two ovarian tubes which ran into them, thus
showing the continuity of the whole. From these facts I
conclude, without hesitation, that the gland itself is a part
of an ovarian tube specially modified; and further, that
the cellular matter, which in the ovarian tubes serves for
the development of the ova, is, by the special action of the
walls of the gland, changed into the opaquer cellular matter
in the ducts, and this again subsequently into that tissue
or substance, which cements the Cirripede to its surface
of attachment.

As the individuals grow and increase in size, so do the
glands and cement-ducts; but it seems often to happen,
that when a specimen is immovably attached, the
cementing apparatus ceases to act, and the cellular contents
of the duct become converted into a thread of
transparent tough cement; the investing membrane, also,
of the ducts, in Conchoderma sometimes becomes hard
and mamillated. I have already alluded to the case of
a Pollicipes, in which both glands and ducts, and even
a small portion of the two adjoining ovarian tubes, had
become thus filled up. As in sessile Cirripedes, at every
fresh period of growth a new cement gland is formed, it
has occurred to me, that possibly in Pollicipes something
similar may take place. In sessile Cirripedes, the old
cement-glands are all preserved in a functionless condition,
adhering to the membranous or calcareous basis,
each new larger one attached to that last formed, and[Pg 36]
each giving out cement-ducts, which, bifurcating in the
most complicated manner, pass outside the shell and thus
attach it to some foreign body.

The cement, removed from the outside of a Cirripede,
consists of a thin layer of very tough, bright-brown,
transparent, laminated substance, exhibiting no structure
under the highest powers, or at most a very fine dotted
appearance, like a mezzotinto drawing. It is of the
nature of chitine; but boiling caustic potash has rather
more effect on it than on true chitine; and I think
boiling nitric acid rather less effect. In one single
instance, namely, in Coronula, the cement comes out of
the four orifices of the two bifurcating ducts, in the
shape of distinct cells, which, between the whale’s skin
and the basal membrane, arrange themselves so as to
make a circular, continuous slip of cement; then the
cells blend together, and are converted into transparent,
structureless cement. Cementing tissue or membrane
would, perhaps, have been a more correct title than
cement; but, in ordinary cases, its appearance is so little
like that of an organised tissue, that I have for this
reason, and for brevity-sake, preferred the simple term of
Cement.

In the larva the cement always escapes through the prehensile
antennæ; and it thus continues to do throughout
life in most or all of the species of Lepas, Conchoderma,
Dichelaspis and Ibla. In the first two of these genera,
the cement escapes from the borders of the lower side of
the disc or penultimate segment of the antennæ, and can
be there seen radiating out like spokes, which at their
ends divide into finer and finer branches, till a uniform
sheet of cement is formed, fastening the antennæ and
the adjoining part of the peduncle down to the surface of
attachment. In Dichelaspis Warwickii and Scalpellum Peronii, the cement, or part at least, comes out of the
ultimate segment of the antennæ, in the shape of one tube,
within another tube of considerable diameter and length.
In Scalpellum vulgare, and probably in some of the other[Pg 37]
species, which live attached to corallines, the cement
soon ceases to debouch from the antennæ, but instead,
bursts through a row of orifices on the rostral margin of
the peduncle (Pl. IX, fig. 7), by which means this margin
is symmetrically fastened down to the delicate, horny
branches of the zoophyte. In Pollicipes, the two cement-ducts,
either together or separately (Pl. IX, fig. 2, 2 a´),
wind about the bottom of the peduncle in the most
tortuous course, at each bend pouring out cement through
a hole in the membrane of the peduncle. In Ibla the
lower part of the peduncle is internally filled by cement,
and thus rendered rigid. In Lepas fascicularis a vesicular
ball of cement surrounding the peduncle is thus formed
(Pl. I, fig. 6), and serves as a float! All these curious,
special adaptations are described under the respective
genera. How the cement forces its way through the
antennæ, and often through apertures in the thick membrane
of the peduncle, I do not understand. I do not
believe, though some appearances favoured the notion,
that the duct itself debouches and divides, at least this
is not the case in Coronula, but only that the internal
chord of cellular matter thus acts and spreads itself out;
nor do I understand how, when the antennæ and immediately
adjoining parts are once cemented down, any more
cement can escape; yet this must take place, as may be
inferred from the breadth of the cemented, terminal portion
of the peduncle in Lepas and Conchoderma; and
from the often active condition in old individuals of the
cementing organs.

I have entered on this subject at some length, (and I
wish I had space for more illustrations,) from its offering,
perhaps, the most curious point in the natural history of
the Cirripedia. It is the one chief character of the Sub-class.
I am well aware how extremely improbable it
must appear, that part of an ovarian tube should be converted
into a gland, in which cellular matter is modified, so
that instead of aiding in the development of new beings,
it forms itself into a tissue or substance, which leaves the[Pg 38]
body[15] in order to fasten it to a foreign support. But on
no other view can the structure, clearly seen by me both
in the mature Cirripede and in the larva, be explained,
and I feel no hesitation in advancing it. I may here
venture to quote the substance of a remark made by Professor
Owen, when I communicated to him the foregoing
facts, namely, that there was a new problem to solve,—new
work to perform,—to attach permanently a crustacean
to a foreign body; and that hence no one could,
a priori, tell by what singular and novel means this would
be effected.

Filamentary Appendages.—These have generally been
considered to act as branchiæ; they occur at the bases of
the first pair of cirri in Lepas, Alepas, Conchoderma,
and in three species of Pollicipes: in Conchoderma there
are similar appendages attached to the pedicels of the
cirri (Pl. IX, fig. 4, g-k); and in the above three species
of Pollicipes there is a double row of them on the prosoma:
their numbers differ in different species (in some there
being none) of the same genus, and even in different individuals
of the same species; they are entirely absent in
the majority of the genera. These facts would indicate
that they are not of high functional importance; and they
seem so generally occupied by testes (Pl. iv, fig. 5), that
I suspect their function is quite as much to give room
for the development of these glands, as to serve for
respiratory purposes. With the exception of the four
above-named genera, the mere surface of the body and
of the sack must be sufficient for respiration: in Conchoderma
aurita the two great expansions of surface, afforded
by the folded, tubular, ear-like projections, aid, as I
believe, towards this end.[Pg 39]

The shape of the body varies, owing to the greater or less
development of the lower part of the prosoma, the greater
or less distance of the first from the second pair of cirri,
and of the mouth from the adductor scutorum muscle,
(Pl. IX, fig. 4, and Pl. IV, 8 a´). In all the genera, the body
is much flattened. I may here mention a few particulars
about the muscular system. One of the largest muscular
masses is formed by the adductor scutorum, and by the
muscles which surround in a double layer (the fasciæ
being oblique to each other) the whole of the upper part
of the prosoma. From under the adductor, a pair of
delicate muscles runs to the basal edge of the labrum, so
as to retract the whole mouth, and two other pair to the
integument between the mouth and the adductor, so as
to fold it: again, there are other delicate muscles in some
(for instance in Lepas Hillii) if not in all the Lepadidæ,
crossing each other in the most singular loops, and serving
apparently to fold the membrane between the occludent
edges of the scuta. Within the prosoma there is a strong
adductor muscle, running straight from side to side, for
the purpose, as it appears, of flattening the body. The
thorax, on the dorsal and ventral surfaces, is well furnished
with straight and oblique muscles (without striæ),
which straighten and curl up this part of the body. The
muscles running into the pedicels of the cirri, cross each
other on the ventral surface of the thorax; the muscles
within the rami are attached to the upper segments of
the pedicels. Finally, I may remark that the whole of the
body and the cirri are capable of many diversified movements.

Mouth.—This is prominent, and almost probosciformed
(Pl. IX, fig. 4 b), and in the abnormal Anelasma
(Pl. IV, fig. 2 d), quite probosciformed,—such, also, was
its character in the larval condition. In outline, it is either
sub-triangular, or oval with the longer axis transverse; the
whole is capable, as well as the separate organs, of considerable
movement, as I have seen in living sessile
Cirripedes. It is composed (Tab. V, fig. 2) of a labrum,[Pg 40]
swollen or bullate, often to such an extent as to equal
in its longitudinal axis the rest of the mouth; of palpi
soldered to the labrum; of mandibles, maxillæ, and outer
maxillæ, the latter serving as a lower lip. These organs
have only their upper segments free, but there are traces,
clearly seen in the mandibles (Pl. X, fig. 1, a, b), of their
being formed of three segments. The two lower segments
are laterally united, and open into each other, the
prominence of the mouth being thus caused: this condition
appears to me curious, and is, to a certain limited
extent, intermediate between those articulated animals
which have their trophi soldered into a proboscis, and
those furnished with entirely free masticatory or prehensile
organs. The palpi adhere to the corners of the labrum;
and I call them palpi only from seeing that they spring
laterally from above the upper articulation of the mandibles.
The prominence of the mouth, measured from
the basal fold by which the whole is separated from the
body, is much greater on the half formed by the labrum
and mandibles, than on the other half facing the cirri.
The trophi surround a cavity—the supra-œsophageal
cavity—in the middle of which, between the mandibles
is seated the orifice of the œsophagus. The œsophagus
is surrounded by long, fine, muscular fasciæ, radiating in
all directions, opposing the constrictor muscles, and is
capable of violent swallowing movements,—constriction
after constriction being seen to run down its whole
course: there are also some fine muscles attached to the
membrane forming the supra-œsophageal cavity. The
trophi serve merely for the prehension of prey, and not
for mastication.

The Labrum, as stated, is always bullate or swollen;
and sometimes the upper exterior part forms, as in
Ibla (Pl. IV, fig. 8 a, c), and Dichelaspis, an overhanging
blunt point. The object, I suspect, of this bullate form
is to give, in the upper part, attachment to longer muscles
running to the lateral surfaces of the mandibles, and
lower down to the œsophagus. The crest close over the[Pg 41]
supra-œsophageal cavity, is generally furnished with small,
often bead-like teeth. The Palpi are small, their apices
never actually touching each other; they are more or
less blunt, not differing much in shape in the different
genera (Pl. X, figs. 6 to 8), and clothed with spines. They
are not capable of movement; their function seems to be
to prevent prey, brought by the cirri, escaping over the
labrum; I infer this from finding in Anelasma and in
the male of Ibla, which have the cirri functionless, that
the palpi are rudimentary.

The Mandibles (Pl. X, figs. 1-5) have from two to
ten strong teeth in a single row; where the number
exceeds five, several of the teeth are small; the inferior
angle is generally pectinated with fine spines;
in Lithotrya (fig. 2), the interspaces between the teeth are
also pectinated. In the same individual there is not unfrequently
one tooth, more or less, on opposite sides of
the mouth. Internally, the mandibles are furnished on
their outer and inner sides with several ligamentous
apodemes, in Lithotrya roughened with points (Pl. X,
fig. 2), for the attachment of the muscles; of these (fig. 1),
there is a chief depressor and elevator, attached at their
lower ends to near the basal fold of the mouth, and a
lateral muscle, attached to the broad basal end of the palpi,
and serving, apparently, to oppose the edge of mandible to
mandible. The Maxillæ in the different genera (Pl. X,
figs. 9 to 15) differ considerably in outline; they are generally
about half the size of the mandibles; at the upper
corner, there are always two or three spines larger than
the others, and often separated from them by a notch;
the rest of the spinose edge is straight, or irregular, or
step-formed, or with the lowest part projecting, or with
one or two narrow prominences bearing fine spines. All
these spines, quite differently from the teeth of the mandibles,
are articulated on the edge of the organ, and stand
in a double row. At a point corresponding with the
upper articulation of the mandibles, a long, thin, narrow,
rigid apodeme, projects inwards (fig. 10), and running[Pg 42]
down nearly parallel to the thin, outer, flexible membrane
of the mouth, is attached to the corium, and thus serves as
a support to the whole organ. This apodeme is embedded
in muscles (Pl. X, fig. 10); there are other large muscles
attached to the inner side of the organ, and again others
running laterally towards the mandibles. The apodeme,
of course, is moulted with the integuments of the mouth.
The Outer Maxillæ (Pl. X, figs. 16, 17) serve as a lower
lip; they are thicker than the other trophi; they have
their inner surfaces clothed with spines, sometimes divided
into an upper and lower group, and occasionally separated
by a deep notch: there are often long bristles outside.
They are furnished with at least two muscles; in sessile
Cirripedes I have seen that they are capable of a rapid
to and fro movement, and I have no doubt that their
function is to brush any small creature, caught by the
cirri, towards the maxillæ, which are well adapted to aid
in securing the prey, and to hand it over to the mandibles,
by them to be forced down the œsophagus. On the exterior
face of the outer maxillæ, above a trace of an upper
articulation, either two small orifices or two large tubular
projections can always be discovered; and these, as will
presently be mentioned, I believe to be olfactory organs.

Cirri.—The five posterior pair are seated close to each
other and equidistant; the first pair is generally seated at a
little distance, and sometimes at a considerable distance
from the second pair. The first pair is the shortest; the
others, proceeding backwards, increase gradually in length.
The rami of each pair are either equal in length or slightly
unequal: those of the first pair are oftenest unequal.
The number of segments in the posterior cirri is sometimes
very great; in one species of Alepas, there were
above sixty segments in one ramus, the other ramus being
in this unique case (Pl. X, fig. 28) small and rudimentary.
The pedicels consist of two segments, a lower, longer, and
upper short one (fig. 18, c, d.) In the usual arrangement
of the spines on the segments of the three posterior pair
of cirri, there are (figs. 26, 27) from three to six pair of[Pg 43]
long spines on the anterior face, with generally some
minute spines (occasionally forming a tuft) intermediate
between them: on the dorsal surface, in the uppermost
part of each segment, there is a tuft of short spines
generally mingled with some longer, finer ones: on the
inner side of each segment, on the upper rim, there are
generally a few extremely minute and short spines. From
the increase of these latter and of the intermediate spines,
the antero-lateral faces of the segments of the first cirrus,
and of the lower segments of the anterior ramus of the
second cirrus (Pl. X, fig. 25), are almost always thickly
paved with brush-like masses of spines. The lower segments
of the anterior ramus of the third cirrus is generally,
though not always, thus paved: these paved segments
are much broader than the others. The posterior rami
of the second and third cirri are often in some slight
degree paved, though in other cases they resemble the
three posterior pair of cirri. The two segments of the
pedicels have bristles on their anterior faces, essentially
arranged on the same plan as on the segments of the
rami: the bristles are generally not so symmetrically
arranged on the pedicels of the second and third cirri, as
on the three posterior pair. There are some exceptions
to the foregoing general rules: in the posterior cirri of
Alepas cornuta, there is only one pair of long spines to
each segment (fig. 28); in Dichelaspis Lowei, there are
eight pair; in Lepas fascicularis, in old specimens, the
segments are paved with a triangular brush of spines;
the upper segments in Pæcilasma eburnea support small
oblong brushes; and, lastly, in Pæcilasma fissa (fig. 29),
and crassa, the spines form a single circle round each
segment, interrupted on the two sides. These spines are
often doubly serrated or plumose: many of them on the
protuberant segments of the first three pair of cirri, are
sometimes coarsely and doubly pectinated.

Caudal Appendages.—These are present (Pl. X,
figs. 18 to 24) seated on each side of the anus, in all the
genera, except in Conchoderma, Anelasma, and Scalpellum villosum;[Pg 44]
they consist of a very small single segment,
destitute of spines in Lepas, and spinose in Pæcilasma,
Dichelaspis, Oxynaspis, Scalpellum, and some species of
Pollicipes; they consist of several segments in Alepas,
Ibla, Lithotrya, and in some species of Pollicipes. In the
latter genus, some species have their caudal appendages
multiarticulate, though so obscurely articulated, that the
passage (fig. 22) from several to one segment is seen to
be easily effected. When the appendage consists of many
articulations, it is generally about as long as the pedicel
of the sixth cirrus; but in Ibla quadrivalvis, it is four
times as long. The segments are narrow, slightly flattened,
much tapering; each (fig. 24) is surmounted by
a ring of short spines, which are generally longest on
the apex of the terminal segment. I could never trace
muscles into these appendages.

Alimentary Canal.—The œsophagus is of considerable
length: it is formed of strong, transparent, much folded
membrane, continuous with the outer integuments, and
moulted with them: it is surrounded by corium, and as
already stated, by numerous muscles: at its lower end it
expands into a bell, with the edges reflexed, and sometimes
sinuous: this bell lies within the stomach, and
keeps the upper broad end expanded. According to the
less or greater distance of the mouth from the adductor
muscle, the œsophagus runs in a more or less parallel
course to the abdominal surface between the first and succeeding
pairs of cirri, and enters the stomach more or less
obliquely. In Ibla alone, it passes exteriorly to, and
over the adductor scutorum muscle. The stomach lies
in a much curved, almost doubled course; it is often a
little constricted where most bent; it is broadest at the
upper end, and here, in Lepas and Conchoderma, there
are some deep branching cæca; in the latter of these
two genera, the whole surface is, in addition, pitted in
transverse lines. The stomach is coated by small,
opaque, pulpy, slightly arborescent glands, believed to be
hepatic; these are arranged in longitudinal lines, in all[Pg 45]
the genera, except in Alepas, in which they are transverse
and reticulated: the whole stomach is thus coated. There
is, also, a coating of excessively delicate, longitudinal and
transverse muscles without striæ. The rectum varies in
length, extending inwards from the anus to between the
bases of the second and fifth pair of cirri: it is narrow,
and formed of much folded transparent membrane, resembling
the œsophagus, continuous with the outer
integuments, with which it is periodically moulted. The
anus is a small longitudinal slit, in the triangular piece of
membrane representing the abdomen, let in between the
last thoracic tergal arches, as already mentioned under the
head of the Metamorphoses; it lies almost between the
caudal appendages, and opens on the dorsal surface.
Within the stomach, there can generally be plainly seen,
in accordance with the period of digestion when the specimen
was taken, a thin, yet strong, perfectly transparent
epithelial membrane, not exhibiting under the highest
power of the microscope any structure: it enters the
branching cæca, and extends from the edge of the bell
of the œsophagus to the commencement of the closed
rectum, and consequently terminates in a point: it consists
of chitine, like the outer integuments of the animal,
and by placing the whole body in caustic potash, I have
dissolved the outer coats of the stomach, and seen the
bag open at its upper end, perfectly preserved, floating
in the middle of the body, and full of the debris of the
food. In most of the specimens which I have examined,
preserved in spirits of wine, this epithelial lining was some
little way distant and separate from the coats of the
stomach; and hence was thought by M. Martin St. Ange
to be a distinct organ, like the closed tube in certain
Annelids. Occasionally, I have seen one imperfect epithelial
bag or tube within another and later-formed one.
Digestion seems to go on at the same rate throughout the
whole length of the stomach; if there be any difference,
the least digested portions lie in the lower and narrower
part. The prey, consisting generally of crustacea, infusoria,[Pg 46]
minute spiral univalves, and often of the larvæ of
Cirripedes, is not triturated: when the nutritious juices
have been absorbed, the rejectamenta are cast out through
the anus, all kept together in the epithelial bag, which is
excluded like a model of the whole stomach, with the
exception of that part coated by the bell of the œsophagus.
I have sometimes thought that the bag was formed so
strong, for the sake of thus carrying out the excrement
entire, so as not to befoul the sack. I believe Lepas can
throw up food by its œsophagus; at least, I found in one
case, many half-digested small Crustaceans in the sack,
and others of the same kind in the stomach.

Circulatory System.—I can add hardly anything to
what little has been given by M. Martin St. Ange: like
others, I have failed, as yet, in discovering a heart. The
whole body is permeated by channels, which have not
any proper coat: there is one main channel along the
ventral surface of the thorax, dividing and surrounding
the mouth, and giving out branches which enter the inner
of the two channels in each cirrus: as Burmeister has
shown, there are also two channels in the penis. There
are two dorso-lateral channels in the prosoma, which are
in direct connection with the great main channel, running
down the rostral (i. e., ventral) side of the peduncle. This
latter main channel branches out in the lower part, and
transmits the fluid through the ovarian tubes, whence, I
believe, it flows upwards and round the sack, re-entering
the body near the sides of the adductor scutorum muscle.
The main rostral channel (or artery?) in the uppermost
part of the peduncle, has a depending curtain, which, I
think, must act as a valve, so as to prevent the circulating
fluid regurgitating into the animal’s body during the contractions
of the peduncle.

Nervous System and Organs of Sense.—In most of the
genera, there are six main ganglia, namely, the supra-œsophageal,
and five thoracic ganglia; but in Pollicipes
mitella there are only four thoracic ganglia. Of these,
the first thoracic or infra-œsophageal ganglion is considerably[Pg 47]
the largest and most massive; it is squarish,
or oval, or heart-shaped; it presents no trace of being
formed by the union of two lateral ganglia. Two great
nerves spring from its under side (A), represented in the
woodcut on page 49, by dotted lines, and run straight
down amongst the viscera in the prosoma: these nerves
are about as large as those forming the collar and those
running to the second ganglion; hence, six great nerves
meet here, two in front, two behind, and two on the
under side. At the anterior end, over the junction with
the collar chord, three equal-sized nerves rise on each side,
with a fourth, smaller one, outside; these go to the
trophi and to the two olfactory sacks. At the posterior
end, on each side, a pair of nerves branch out rectangularly,
one of which (a,) goes to the first cirrus, and there
divides into two branches; of these, the upper runs up
the cirrus, and the lower one downwards. The other
nerve (b), proceeding on each side from this first thoracic
ganglion, runs to the muscles beneath the basal articulation
of the first cirrus. The collar surrounding the œsophagus
is generally very long, sometimes equalling the
whole thoracic chord; at a middle point, a small branch
is sent off, and at the anterior end (e, e), close to the
supra-œsophageal ganglia, double or treble fine branches
run to the true ovaria, lying close to the upper end of the
stomach. The four (or only three) other thoracic ganglia,
when viewed as transparent bodies, are seen to be solid;
but in some of the genera, as in Conchoderma, the outline
plainly shows, that each consists of a lateral pair fused
together. The second thoracic ganglion (B) is rather
small; it is either close to the first, as in Pollicipes
mitella and Lepas fascicularis, or far distant, as in Ibla.
The third (C) and fourth are of about the same size with
the second: these three ganglia send large branches to
the second, third, and fourth pair of cirri: other minute
branches spring from their under sides, and from the
intermediate double chords. The fifth ganglion is larger
and longer than the three preceding ones, and gives off[Pg 48]
nerves to the fifth and sixth pair of cirri; it is clearly
formed by the union of the fifth, with what ought to have
formed a sixth ganglion. The two nerves going to the
sixth cirrus give off on their inner sides, each a great
branch to the penis. In Pollicipes mitella, in which
there are only four instead of five thoracic ganglia, it is
evident from the outline and position of the nerves going
to the fourth pair of cirri, that the fourth ganglion is
fused into the fifth, itself, as we have just seen, normally
composed of two consecutive ganglia. In this
Pollicipes there is other evidence of concentration in
the nervous system, for none of the ganglia show signs
of being formed of lateral pairs; the second is close to
the first; and the abdominal double chord is in part
separated by a mere cleft; lastly, as we shall immediately
see, the same remark is applicable to the supra-œsophageal
ganglia.

The latter (D) alone remain to be described; they
present far more diversity in shape than do the thoracic
ganglia; they are almost always seen in outline to be
laterally distinct, and usually resemble two pears with
their tapering ends cut off and united; in a transverse
line they are as long as the infra-œsophageal ganglion,
but are much less massive. In Lepas fascicularis (D),
they are pear-shaped; in Pollicipes mitella they are
globular, and separated by a third globular ganglion,
which I believe is the ophthalmic ganglion, presently
to be described; in Pollicipes spinosus, however, the
ophthalmic ganglion is, as usual, placed in advance of
the supra-œsophageal ganglion, which latter, in this one
species, shows no sign of being formed of a lateral pair
fused together. In Alepas cornuta the supra-œsophageal
ganglion consists of two quite distinct ganglia, elongated
in the longitudinal axis of the body, and separated from
each other by the whole width of the mouth; the chord
which unites them is of the same thickness as the rest of
the collar. In all the genera, from the front of each
of the two supra-œsophageal ganglia, a pair of nerves,[Pg 49]
(f, f,) united and together as large as the collar nerve,
rises, and can be traced running unbranched, in a nearly
straight line, for a length equalling the whole rest of the
nervous chord, so as to supply the peduncle and the inside
of the capitulum or sack. At the inner ends of these two
same ganglia, from a central point where they are united,
a little central branch runs in front to the adductor
scutorum and other adjoining muscles; and still smaller
fibrils run behind to the œsophageal muscles.

Diagram of the anterior portion of the nervous system in Lepas fascicularis.
A. First thoracic or infra-œsophageal ganglion. B. Second thoracic.
C. Third thoracic ganglion. D. Supra-œsophageal ganglion. E. The two
ophthalmic ganglia. F. Double eye. a. Nerve going to first cirrus; b, to
the muscles below the first cirrus; c, to the second cirrus; d, to the third;
e, nerves running to the ovaria; f, double nerves supplying the sack and
peduncle.

Ophthalmic Ganglia and Eyes.—Owing to Professor
Leidy’s[16] discovery of eyes in a Balanus, I was led to
look for them in the Lepadidæ. Extending from the front
of the two supra-œsophageal ganglia, two chords may be
seen in Lepas fascicularis (of which a rude diagram is
here given), to run into two small, perfectly distinct oval[Pg 50]
ganglia (E), which are not united by any transverse commissure.
From the opposite ends of these two ganglia
smaller nerves run, and, bending inwards at right angles,
enter, beyond the middle, an elongated (F), almost black,
eye, composed of two eyes united together. Although in
outline the eye appears single, two lenses can be distinctly
seen at the end, directed upwards and towards the
ganglia; two pigment-capsules can also be distinguished;
these are deep and cup-formed, and of a dark reddish-purple.
The following measurements will show the proportions
of the parts in a specimen of the Lepas fascicularis
having a capitulum 4/10ths of an inch in length.

In Conchoderma aurita the ophthalmic ganglia are
much smaller, and nearer to the supra-œsophageal ganglion,
than in L. fascicularis. In Alepas cornuta the
ophthalmic chords run towards each other from the two
distant and separate supra-œsophageal ganglia; and the
ophthalmic ganglia, (instead of being quite separate, as in
L. fascicularis,) are united by their front ends, and the
two eyes instead of standing some way in front, with
nerves running to them, are embedded on the double ophthalmic
ganglion; the pigment-capsules here, also, have
the shape of mere saucers, and are joined back to back,
with the two lenses projecting far out of them. In neither
sex of Ibla could I perceive that the eye was double. In
Pollicipes spinosus the ophthalmic ganglion stands in
front of the single supra-œsophageal ganglion, and shows
no signs of being formed of a lateral pair; the eyes themselves,
however, differently from, in all the foregoing cases,
are, though approximate, quite distinct. In Pollicipes[Pg 51]
mitella I did not see the eyes; but the ophthalmic ganglion
consists, as I believe, of a single globular one, placed
exactly between the two globular, supra-œsophageal ganglia,
all three being of nearly equal size. Professor Leidy
does not mention the ophthalmic ganglia; hence I infer
that in Balanus, which is a more highly organised Cirripede,
they are fused into the supra-œsophageal ganglion.

In all the genera, the double eye is seated deep within
the body; it is attached by fibrous tissue to the radiating
muscles of the lowest part of the œsophagus, and lies
actually on the upper part of the stomach; consequently,
a ray of light, to reach the eye, has to pass through the
exterior membrane and underlying corium connecting the
two scuta, and to penetrate deeply into the body. In
living sessile Cirripedes, vision seems confined to the
perception of the shadow of an object passing between
them and the light; they instantly perceived a hand
passed quickly at the distance of several feet between a
candle and the basin in which they were placed.

As the infra-œsophageal ganglion sends nerves to the
trophi and to the first pair of cirri, it must correspond
to the segments, from the fourth to the ninth inclusive,
of the archetype crustacean. The state of the supra-œsophageal
and ophthalmic ganglia appears to me very
interesting: I do not believe that in any mature ordinary
crustacean, the first or ophthalmic ganglion can be shown
to be distinct from the two succeeding ganglia, or to be
itself composed of a pair laterally distinct. The ganglia,
corresponding with the second and third segments of the
body, which should normally support two pair of antennæ,
are in the Lepadidæ united together; but laterally they
are generally distinct in outline, and are actually separate
in Alepas: the supra-œsophageal ganglion shows also its
double nature, by giving rise to a pair of large double
nerves, evidently corresponding with the two pair of antennular
nerves in ordinary crustaceans. The embryonic
condition of the whole supra-œsophageal portion of the
nervous system in the Lepadidæ, corresponds with the[Pg 52]
rudimentary state of the only organ of sense supplied by
it, namely, the eye, which in size and general appearance
has retrograded to the state in which it was in,
during the first stage of development of the larva;—I
have used the term embryonic, because, in the embryos of
ordinary crustacea, all the ganglia are at first longitudinally
distinct, and laterally quite separate. The conclusion
at which we before arrived from studying the metamorphoses,
namely, that the whole peduncle and capitulum
consisted of the first three segments of the head, is beautifully
supported by the structure of the nervous system,
in which these parts are seen to be supplied with nerves
exclusively from the supra-œsophageal ganglion: now in
ordinary crustacea the supra-œsophageal ganglion sends
nerves to the eyes and the two pair of antennæ corresponding,
as is known by embryological dissections, to the first
three segments of the body. Moreover, it is asserted that
the carapace which covers the thorax in crustacea, is not
formed by the development of the first segment; and this,
likewise, may be inferred to be the case with the peduncle
and capitulum in the Lepadidæ, as the nerves
of the ophthalmic ganglia go exclusively to the eyes.
Finally, I may remark that in Pollicipes, looking to the
whole nervous system, the state of concentration nearly
equals that in certain macrourous decapod crustaceans,
for instance the Astacus marinus, of which a figure is given
by Milne Edwards.

Olfactory Organs.—In the outer maxillæ, at their bases
where united together, but above the basal fold separating
the mouth from the body, there are, in all the genera,
a pair of orifices (Pl. X, fig. 16); these are sometimes
seated on a slight prominence, as in Lithotrya, or on the
summit of flattened tubes (Pl. X, fig. 17), projecting upwards
and towards each other, as in Ibla, Scalpellum,
and Pollicipes. In Ibla these tubular projections rise from
almost between the outer and inner maxillæ. It is impossible
to behold these organs, and doubt that they are of
high functional importance to the animal. The orifice leads[Pg 53]
into a deep sack lined by pulpy corium, and closed at the
bottom. The outer integument is inflected inwards, (hence
periodically moulted,) and becoming of excessive tenuity,
runs to near the bottom of the sack, where it ends in an
open tube: so excessively thin is this inflected membrane,
that, until examining Anelasma, I was not quite certain
that I was right in believing that the outer integument
did not extend over the whole bottom. I several times
saw a nerve of considerable size entering and blending
into a pulpy layer at the bottom of the sack of corium;
but I failed in tracing to which of the three pair of
nerves, springing from the front end of the infra-œsophageal
ganglion, it joined. I can hardly avoid concluding,
that this closed sack, with its naked bottom, is an organ
of sense; and, considering that the outer maxillæ serve
to carry the prey entangled by the cirri towards the
maxillæ and mandibles, the position seems so admirably
adapted for an olfactory organ, whereby the animal could
at once perceive the nature of any floating object thus
caught, that I have ventured provisionally to designate
the two orifices and sacks as olfactory.

Acoustic (?) Organs.—A little way beneath the basal
articulation of the first cirrus (Pl. IX, fig. 4 d, and Pl. IV,
fig. 2 e), on each side, there may be seen a slight swelling,
and on the under side of this, a transverse slit-like orifice,
1/20th of an inch in length in Conchoderma, but often only
half that size. In Ibla this orifice is seated lower down
(Pl. IV, fig. 8 a´, e), between the bases of the first and
second cirri, which are here far apart: in Alepas cornuta
it is placed rather nearer to the adductor scutorum
muscle, namely, beneath the mandibles. The orifice leads
into a rather deep and wide meatus; the external integument
is turned in for a short distance, widening a little,
and then ends abruptly. The meatus, enlarging upwards,
is lined by thick pulpy corium, and is closed at the upper
end; from its summit is suspended a flattened sack of
singular and different shapes in the different genera.
This, the so-called acoustic sack of Conchoderma virgata,[Pg 54]
is figured Pl. IX, fig. 6. The deep and wide notch faces
towards the posterior end of the animal; the inferior lobe,
thus almost cut off, is flattened in a different plane from
the upper part; the lobe is lodged in a little pouch of corresponding
form, leading from the open meatus in which
the upper part is included. In Conchoderma aurita, the
top of the acoustic sack is narrower and more constricted,
the whole more rounded, and the lobe more turned down.
In Lepas fascicularis the notch is not so deep or wide,
and the lobe larger. In Ibla Cumingii the sack is of the
shape of a vase, with one corner folded over. In Scalpellum
vulgare it is small, oval, with the lower end much
pushed in, and furnished with a little crest. Lastly, in
Pollicipes mitella it is simply oval. In all cases the sack
is empty, or contains only a little pulpy matter: it
consists of brownish, thick, and remarkably elastic tissue,
formed, apparently, of transverse little pillars, becoming
fibrous on the outside, and with their inner ends appearing
like hyaline points. The mouth of the acoustic sack
(removed in the drawing) is closed by a tender diaphragm,
through which I saw what I believe was a moderately-sized
nerve enter; I have not yet succeeded in tracing
this nerve. The first pair of cirri seem, to a certain extent,
to serve as antennæ, and therefore the position of an
acoustic organ at their bases, is analogous to what takes
place in crustacea; but there are not here any otolites,
or the siliceous particles and hairs, as described by Dr.
Farre, in that class. Nevertheless, the sack is so highly
elastic, and its suspension in a meatus freely open to the
water, seems so well adapted for an acoustic organ, that
I have provisionally thus called it. In the larva, as I
have shown, a pouch, certainly serving for some sense,
I believe for hearing, is seated in quite a different
position at the anterior end of the carapace. I may
mention that I found sessile Cirripedes very sensitive of
vibrations in objects adjoining them, though not, apparently,
of noises in the air or water. In a group of
specimens, I could not touch one even most delicately[Pg 55]
with a needle, without all the adjoining ones instantly
withdrawing their cirri; it made no difference
if the one touched had its operculum already closed and
motionless.

Reproductive System,—Male Organs.—All the Cirripedia
which I have hitherto examined, with the exception
of certain species of Ibla and Scalpellum, are hermaphrodite
or bisexual.[17] I shall so fully describe the
sexual relations of the several species of these two genera,
under their respective headings, and at the end of the
genus of Scalpellum, that I will not here give even an
abstract of the grounds on which my firm belief is based,
that the masculine power of certain hermaphrodite species
of Ibla and Scalpellum, is rendered more efficient by
certain parasitic males, which, from their not pairing,
as in all hitherto known cases, with females, but with
hermaphrodites, I have designated Complemental Males.

The male organs have been well described by
M. Martin St. Ange, whose observations have since been
confirmed by R. Wagner.[18] The testes are small,
often leaden-coloured, either pear or finger-shaped, or
branched like club-moss,—these several forms sometimes
occurring in the same individual; they coat the stomach,
enter the pedicels, and even the basal segments of the
rami of the cirri, and in some genera occupy certain[Pg 56]
swellings on the thorax and prosoma, and in others the filamentary
appendages: the testes seen in the apex in one of
these appendages in Conchoderma, is represented in Pl. IX,
fig. 5. The two vesiculæ seminales are very large; they
lie along the abdominal surface of the thorax, and generally
(but not in some species of Scalpellum) enter the
prosoma, where their broad ends are often reflexed; here
the branched vessels leading from the testes enter. The
membrane of the vesiculæ seminales is formed of circular
fibres; and is, I presume, contractile, for I have seen the
spermatozoa expelled with force from the cut end of a
living specimen. The two canals leading from the vesiculæ
generally unite in a single duct at the base of the
penis; but in Conchoderma aurita, half-way up it. The probosciformed
penis, except in certain species of Scalpellum,
is very long; it is capable of the most varied movements;
it is generally hairy, especially at the end; it is supported
on a straight unarticulated basis, which in Ibla quadrivalvis
alone (Pl. IV, fig. 9 a), is of considerable length;
in this species, the upper part is seen to be as plainly
articulated as one of the cirri; in Alepas, the articulations
are somewhat less plain, and in the other genera,
the organ can be said only to be finely ringed, but these
rings no doubt are in fact obscure articulations. In the
females of Ibla Cumingii and Scalpellum ornatum, there
is, of course, no penis.

Female Organs.—M. Martin St. Ange has described
how the peduncle[19] is gorged with an inextricable mass
of branching ovarian tubes, filled with granular matter
and immature ova. In Conchoderma and Alepas, the
ovarian tubes run up in a single plane (Pl. IX, fig. 3,)
between the two folds of corium round the sack. Here
the development of the ova can be well followed: a
minute point first branches out from one of the tubes; its[Pg 57]
head then enlarges, like the bud of a tulip on a footstalk;
becomes globular; shows traces of dividing, and at last
splits into three, four, or five egg-shaped balls, which
finally separate as perfect ova. Within the peduncle,
the ovarian tubes branch out in all directions, and within
the footstalks of the branches (differently from what
takes place round the sack), ova are developed, as well
as at their ends. Close together, along the rostral
(i. e., ventral) edge of the peduncle, two nearly straight,
main ovarian tubes or ducts may be detected, which do
not give out any branches till about half way down the
peduncle, where they subdivide into branches, which inosculate
together, and give rise to the mass filling the
peduncle, and sometimes, as we have just seen, sending up
branches round the sack. These two main unbranched
ovarian ducts, followed up the peduncle, are seen to
enter the body of the Cirripede (close along side the
great double peduncular nerves), and then separating,
they sweep in a large curve along each flank of the prosoma,
under the superficial muscles, towards the bases of
the first pair of cirri; and then rising up, they run into
two glandular masses. These latter rest on the upper
edge of the stomach, and touch the cæca where such exist;
they were thought by Cuvier to be salivary glands. They
are of an orange colour, and form two, parallel, gut-formed
masses, having, in Conchoderma, a great flexure,
and generally dividing at the end near the mouth into
a few blunt branches. I was not able to ascertain
whether the two main ducts, coming from the peduncle,
expanded to envelope them, or what the precise connection
was. The state of these two masses varied
much; sometimes they were hollow, with only their
walls spotted with a few cellular little masses; at other
times they contained or rather were formed of, more or
less globular or finger-shaped aggregations of pulpy matter;
and lastly, the whole consisted of separate pointed
little balls, each with a large inner cell, and this again
with two or three included granules. These so closely[Pg 58]
resembled, in general appearance and size, the ovigerms
with their germinal vesicles and spots, which I have often
seen at the first commencement of the formation of the
ova in the ovarian tubes in the peduncle, that I cannot
doubt that such is their nature. Hence I conclude,
that these two gut-formed masses are the true ovaria.
I may add, that several times I have seen in the two
long, unbranched ducts, connecting the true ovaria and the
ovarian tubes in the peduncle, pellets of orange-coloured
cellular matter (i. e., ovigerms) forming at short intervals
little enlargements in the ducts, and apparently travelling
into the peduncle.

The structure here described is quite conformable with
that which we have seen in the larva; in the latter, two
gut-formed masses of equal thickness extended from the
cæca of the stomach to within the future peduncle, where
the cement-ducts entered them, and where, after a short
period, they were seen to expand into a mass of ovarian
tubes. In the mature Cirripede, the cement-ducts can
still be found united to the ovarian tubes in the middle of
peduncle; and the cause of the wide separation of the true
ovaria and ovarian tubes, can be simply accounted for by
the internal, almost complete intersection of the animal,
which takes place during the last metamorphosis.

The ova, when excluded, remain in the sack of the
animal until the larvæ are hatched; they are very numerous,
and generally form two concave, nearly circular,
leaves, which I have called after Steenstrup and other
authors, the ovigerous lamellæ (Pl. IV, fig. 2 b). These
lamellæ lie low down on each side of the sack: in Conchoderma
virgata, however, there is often only a single lamella,
forming a deeply concave cup: in C. aurita there are generally
on each side four lamellæ, one under the other. The
ova lie in a layer from two to four deep; and all are held
together by a most delicate transparent membrane, which
separately enfolds each ovum: this membrane is often
thicker and stronger round the margins of the lamellæ,
where they are united, in a peculiar manner, presently to be[Pg 59]
described, to a fold of skin, on each side of the sack: these
two folds, I have called the ovigerous fræna (Pl. IV, fig. 2 f).

M. Martin St. Ange, describes an orifice under the
carina, by which he supposes the ova to enter the sack;
this, after repeated and most careful examinations, I venture
to affirm does not exist; on the contrary, I have
every reason to believe that the ova enter the sack in the
following curious manner. Immediately before one of
the periods of exuviation, the ova burst forth from the
the ovarian tubes in the peduncle and round the sack,
and, carried along the open circulatory channels, are collected
(by means unknown to me) beneath the chitine-tunic
of the sack, in the corium, which is at this period
remarkably spongy and full of cavities. The corium
then forms or rather (as I believe) resolves itself into the
very delicate membrane separately enveloping each ovum,
and uniting them together into two lamellæ; the corium
having thus far retreated, then forms under the lamellæ
the chitine-tunic of the sack, which will of course be of
larger size than the last-formed one, now immediately to
be moulted with the other integuments of the body. As
soon as this exuviation is effected, the tender ova, united
into two lamellæ, and adhering, as yet, to the bottom
of the sack, are exposed: as the membranes harden, the
lamellæ become detached from the bottom of the sack, and
are attached to the ovigerous fræna. To demonstrate this
view, an individual should have been found, with both the
old and new chitine tunic of the sack, and with the lamellæ
lying between them; this, I believe, I have seen, but it
was before I understood the full importance of the fact:
a great number of specimens would have to be examined
in order to succeed again, for the changes connected with
exuviation supervene very quickly. I have, however,
several times found the ova so loose under the sack, as
to be detached with a touch from the ovarian tubes;
and I have twice carefully examined specimens, which
had just moulted, as shown by even the mandibles being
flexible, in which the lamellæ had not become united to[Pg 60]
the fræna, but still adhered to the newly-formed chitine
tunic of the sack; in these, the ova were so tender, that
they broke into pieces rather than be separated from the
membrane of the lamella, itself hardly perfectly developed,
for pulpy cellular matter adhered outside some of
the ova. These and other facts are quite inexplicable on
any other view than that advanced.

As the lamellæ are formed without organic union
with the parent, they would be liable to be washed out
of the widely open sack of the Lepadidæ, if they had
not been specially attached to the fræna. These fræna
consist of a pair of more or less semicircular folds of
skin, depending inside the sack, on each side of the point
of attachment of the body. The fræna are often of considerable
size, but in Ibla, they are very minute; they are
formed of chitine tunic with underlying corium, like the
rest of the sack; on their crests, there is a row, or a set
of circular groups, or a broad surface, covered, either
with minute, pointed, bead-like bodies mounted on long
hair-like footstalks, or with staff-formed bodies on very
short footstalks. I measured some of the bead-like bodies,
in Lepas anserifera, and they were 1/2000th of an inch in
diameter, and the footstalks three or four times as long
as the elongated heads. These heads, of whatever shape
they may be, have an opaque, and, I believe, glandular
centre; I could not make out with certainty an aperture
at their ends, but, I believe, such exists, and they seem to
secrete a substance, which hardens into a strong membrane,
serving to unite the crest of the frænum to the edges of
the lamellæ. In one case, this bit of membrane seemed
formed of a woven mass of threads. These little glandular
bodies, with the membrane formed by them, are
cast off at each exuviation, and new glands formed on the
crest of the frænum underneath. In some species of
Pollicipes, (viz., P. cornucopia and elegans,) the fræna,
though present and large, are functionless and destitute
of the glands: I believe, they exist in this same functionless
condition, and in rather a different position in the[Pg 61]
sessile Cirripedes, and that in this family they serve as
Branchiæ.

The above-described method by which Cirripedia lay
their eggs, namely, united together in a common membrane,
placed between their old outer and new inner
integuments, and the manner in which the lamellæ,
when thus formed, are retained for a time fastened to
the fræna, and are then cast off, appears to me very
curious. In some of the lower Crustacea, it is known,
that the ova escape by rupturing the ovisacs formed
by the protruded ovarian tubes, and this is the nearest
analogy with which I am acquainted. The ova are
impregnated (as I infer from the state of the vesiculæ
seminales), when first brought into the sack, and whilst
the membrane of the lamellæ is very tender: the long
probosciformed penis seems well adapted for this end.
In the male of Ibla Cumingii, which has not a probosciformed
penis, the whole flexible body, probably, performs
the function of the penis: in Scalpellum ornatum, however,
the spermatozoa must be brought in by the action of the
cirri, or of the currents produced by them. That cross impregnation
may and sometimes does take place, I infer
from the singular case of an individual, in a group of
Balani, in which the penis had been cut off, and had
healed without any perforation; notwithstanding which
fact, larvæ were included in the ova.

Exuviation; Rate of Growth; Size.—I have had
occasion repeatedly to allude to the exuviation of the
Lepadidæ: with the exception of the genus Lithotrya,[20] in
which the calcareous scales on the peduncle, together
with the membrane connecting them, is cast off, neither
the valves nor the membrane uniting them, nor that
forming the peduncle with its scales and styles, are[Pg 62]
moulted; but the surface gradually disintegrates and is
removed, perhaps sometimes in flakes, whilst new and
larger layers are formed beneath. In Scalpellum, I ascertained
that the new membrane, connecting together the
newly-formed calcified rims under the valves of the capitulum,
was formed as a fold, with the articulated spines
which it bears, all adpressed in certain definite directions.
This fold of new membrane, when the old membrane
splits and yields, of course expands, and thus the size of
the capitulum is increased. In the peduncle, lines of
splitting can seldom be perceived, except, indeed, in the
sub-globular, embedded, downward-growing peduncle of
Anelasma, as described under that genus. I do not
understand what determines the complicated lines of
splitting of the old membrane between the several valves
of the capitulum,—without it be simply, that along these
lines alone, the old membrane is not strengthened by the
new membrane being closely applied under it, the new
being formed, as we have just said, in a fold, in order to
allow of increase in size. Although, as I believe, there is
strictly no exuviation in the outer membranes of mature
Lepadidæ, it seems that narrow strips of membrane are
cast off from between the valves, for the few first moults,
after the final metamorphosis of the larva. I may here
remark that, in most sessile Cirripedes, the outside membrane
connecting the operculum and shell, is regularly
moulted.

The delicate tunic lining the sack, (a mere duplicature
of that thick one, forming the outside of the capitulum,
and generally transformed into valves,) and the integuments
of the whole body, are regularly moulted. With these
integuments, the membrane lining the œsophagus, the
rectum, and the deep olfactory pouches, and the horny
apodemes of the maxillæ, are all cast together. I have
seen a specimen of Lepas, in which, from some morbid
adhesion, the old membrane lining one of the olfactory
pouches had not been moulted, but remained projecting
from the orifice as a brown shrivelled scroll. The new[Pg 63]
spines on the cirri (and on the maxillæ) are formed within
the old ones; but as they have to be a little longer than
the latter, and as they cannot enter these up to their
very points, their basal portions are not thus included,
but are formed, running obliquely across the segments
of the cirri; and what is curious, these same basal portions
are turned inside out, like the fingers of a glove
when hastily drawn off. After the exuviation of the old
spines, the new spines have their inverted basal portions
drawn out from within the segments, and turned outside
in, so as to assume their proper positions.

All Cirripedia grow rapidly: the yawl of H. M. S.
Beagle was lowered into the water, at the Galapagos
Archipelago, on the 15th of September, and, after an
interval of exactly thirty-three days, was hauled in: I
found on her bottom, a specimen of Conchoderma virgata
with the capitulum and peduncle, each half an inch in
length, and the former 7/20ths in width: this is half the size
of the largest specimen I have seen of this species: several
other individuals, not half the size of the above, contained
numerous ova in their lamellæ, ready to burst
forth. Supposing the larva of the largest specimen became
attached the first day the boat was put into the water,
we have the metamorphosis, an increase of length from
about .05, the size of the larva, to an whole inch, and the
laying of probably several sets of eggs, all effected in thirty-three
days. From this rapid growth, repeated exuviations
must be requisite. Mr. W. Thompson, of Belfast, kept
twenty specimens of Balanus balanoides, a form of much
slower growth, alive, and on the twelfth day he found
the twenty-first integument, showing that all had moulted
once, and one individual twice within this period. I
may here add, that the pedunculated Cirripedes never
attain so large a bulk as the sessile; Lepas anatifera is
sometimes sixteen inches in length, but of this, the far
greater portion consists of the peduncle. Pollicipes
mitella is the most massive kind; I have seen a specimen
with a capitulum 2.3 of an inch in width.[Pg 64]

Affinities.—Considering the close affinity between the
several genera, there are, I conceive, no grounds for
dividing the Lepadidæ into sub-families, as has been
proposed by some authors, who have trusted exclusively
to external characters. In establishing the eleven genera
in the Lepadidæ, no one part or set of organs affords
sufficient diagnostic characters: the number of the valves
is the most obvious, and one of the most useful characters,
but it fails when the valves are nearly rudimentary,
and when they are numerous: the direction of their
lines of growth is more important, and fails to be characteristic
only in Scalpellum: with the same exception, the
presence or abscence of calcified or horny scales on the
peduncle is a good generic character. For this same
end, the shape of the scuta and carina, but not of the
other valves, comes into play. In three genera, the presence
of filamentary appendages on the animal’s body is
generic; in Pollicipes, however, they are found only on
three out of the six species. The number of teeth in the
mandibles, and the shape of the maxillæ, often prove
serviceable for this end; as does more generally the
presence of caudal appendages, and whether they be
naked or spinose, uniarticulate or multiarticulate; in
Pollicipes alone this part is variable, being uni-and multi-articulate;
and in one species of Scalpellum they are
absent, though present in all the others. The shape of
the body, the absence or presence of teeth on the labrum,
the inner edge of the outer maxillæ being notched or
straight, the prominence of the olfactory orifices, the
arrangement of the spines on the cirri, and the number
and form of their segments, are only of specific value.

Comparing the pedunculated and sessile Cirripedes, it is,
I think, impossible to assign them a higher rank than that
of Families. The chief difference between them consists,
in the Lepadidæ, in the presence of three layers of striæ-less
muscles, longitudinal, transverse and oblique, continuously
surrounding the peduncle, but not specially attached to
the scuta and terga; and on the other hand, in the Balanidæ,[Pg 65]
of five longitudinal bundles of voluntary muscles,
with transverse striæ, fixed to the scuta and terga, and
giving them powers of independent movement. In the
Lepadidæ, the lower valves, or when such are absent, the
membranous walls of the capitulum, move with the scuta
and terga when opened or shut; and the lower part of the
capitulum is separated by a moveable peduncle from the
surface of attachment; in the sessile Cirripedes, the
lower valves are firmly united together into an immovable
ring, fixed immovably on the surface of attachment. I
will not compare the softer parts, such as the cirri and
trophi, of the Lepadidæ with those of the Balanidæ, as
my examination of this latter family is not fully completed:
I will only remark, that there is a very close
general resemblance, more especially with the sub-family
Chthamalinæ.

Geographical Range; Habitats.—The Pedunculated
Cirripedes extend over the whole world; and most of the
individual species have large ranges, more especially, as
might have been expected, those attached to floating
objects; excepting these latter, the greater number inhabit
the warmer temperate, and tropical seas. Of
those attached to fixed objects, or to littoral animals,
it is rare to find more than three or four species in
the same locality. On the shores of Europe I know of
only three, viz., a Scalpellum, Pollicipes, and Alepas.
At Madeira (owing to the admirable researches of the
Rev. R. T. Lowe), two Pæcilasmas, a Dichelaspis, and an
Oxynaspis are known. In New Zealand, there are two
Pollicipes and an Alepas, and, perhaps, a fourth form.
From the Philippine Archipelago, in the great collection
made by Mr. Cuming, there are a Pæcilasma, an Ibla,
a Scalpellum, Pollicipes, and Lithotrya. Of all the
Lepadidæ, nearly half are attached to floating objects, or
to animals which are able to change their positions; the
other half are generally attached to fixed organic or inorganic
bodies, and more frequently to the former than
to the latter. Most of the species of Scalpellum are inhabitants[Pg 66]
of deep water; on the other hand, most of
Pollicipes,[21] of Ibla, and Lithotrya are littoral forms. The
species of Lithotrya have the power of excavating burrows
in calcareous rocks, shells, and corals; and the singular
manner in which this is effected, is described under that
genus. Anelasma has its sub-globular peduncle deeply
embedded in the flesh of Northern Sharks; and I have
seen instances of the basal end of the peduncle of Conchoderma
aurita, being sunk into the skin of Cetacea; in
the same way the point of the peduncle in the male of
Ibla, is generally deeply embedded in the sack of the
female. I believe in all these cases, the cementing substance
affects and injures the corium or true skin of the
animal on which the creature is parasitic, whilst the surrounding
parts, being not injured, continue to grow
upwards, thus causing the partial embedment of the
Cirripede. In the case of Anelasma, we have growth at
the end of the peduncle, and consequently downward
pressure, and this may possibly cause absorption to take
place in the skin of the shark at the spot pressed on.

Geological History.—Having treated this subject at
length, in the volume of the Palæontographical Society
for 1851, I will not here enter on it: I will only remark,
that the Lepadidæ or Pedunculated Cirripedes are much
more ancient, according to our present state of knowledge,
than the Balanidæ. The former seem to have
been at their culminant point during the Cretaceous
Period, when many species of Scalpellum and Pollicipes,
and a singular new genus, Loricula, existed;
Pollicipes is the oldest genus, having been found in the
Lower Oolite, and, perhaps, even in the Lias. The fossil
species do not appear to have differed widely from
existing forms.[Pg 67]

Genus—Lepas. Plate I.

Valvæ 5, approximatæ: carina sursùm inter terga
extensa, deorsùm aut furcâ infossâ aut disco externo
terminata: scuta subtriangula, umbonibus ad angulum
rostralem positis.

Valves 5, approximate: carina extending up between
the terga, terminating downwards in an embedded fork,
or in an external disc: scuta sub-triangular, with their
umbones at the rostral angle.

Filaments seated beneath the basal articulation of the
first cirri; mandibles with five teeth; maxillæ step-formed;
caudal appendages uniarticulate, smooth.

Description.—Capitulum flattened, sub-triangular,
composed of five approximate valves. The valves are[Pg 68]
either moderately thick and translucent, or very thin and
transparent; and hence, though themselves colourless, they
are often coloured by the underlying corium. Their surfaces
are either smooth and polished, or striated, or furrowed,
and sometimes pectinated. They are not subject
to disintegration; they are generally naked, except on the
borders, where they are coated, and held together by
membrane; in L. fascicularis, however, the valves are
covered with thin membrane, bearing very minute spines.
The manner of growth of the valves will be best described
under each. All the valves, even in the same
species, are subject to considerable variation in shape,
more especially the terga.

Scuta.—These valves are sub-triangular in outline,
with the basal margin straight and rather short; and
with occludent and tergo-carinal margins more or less
protuberant; in L. fascicularis, however, the basal (Pl. I,
fig. 6), and occludent margins are slightly reflexed and
prominent. A ridge, generally runs from the umbo to the
upper point. Internally, there is no conspicuous pit for the
adductor muscle; under the umbones, there is generally
either on both valves, or only on the right-hand side
(Pl. I, fig. 1 c), a small calcareous projection or tooth, of
variable size and shape, even in the same species; it is
generally largest on the right-hand valve; these teeth at
first sight appear to form a hinge, uniting the opposite
scuta at their umbones, but this is not really the case,
and their use appears to be only to give attachment to
the membrane uniting the valves together, and to the
peduncle. The basal margin is internally strengthened
by a calcified rim, more or less developed. The umbones
(and primordial valves when distinguishable,) are seated
at the rostral angles; during growth the basal margin
is not added to, and the occludent margin only to small
extent; hence the main growth of the valve is at the
upper end, and along the carina-tergal margin. In
L. fascicularis, however, the basal reflexed margin is
slightly added to beneath the umbo.[Pg 69]

Terga,—flat, small compared with the scuta, usually of
an irregular quadrilateral figure, with the two upper or
occludent margins very short, in proportion to the two
(carinal and scutal) lower margins; all the margins are
nearly straight. The two occludent margins, generally
meet each other at about right angles, forming a small
triangular projection; in L. fascicularis, however, the
occludent margin is formed by a single, slightly curved line.
The umbones (and primordial valves when distinguishable)
are not seated at the uppermost point, but at the angle
where the carinal margin unites to the upper of the two
occludent margins: during growth the terga are added
to, both on the occludent and on the scutal margins, and
slightly along the carinal margin; hence their growth is
unequally quaqua-versal, except at one angle of the irregular
quadrilateral figure.

Carina.—This is always very narrow and curved, concave
within, often carinated and barbed exteriorly; it extends
upwards between the terga for one half or two
thirds of their length: at the lower extremity it ends
(with the exception of L. fascicularis), in a small fork
(Pl. I, fig. 1, a, b) rectangularly inflected and embedded
in the membrane, beneath the basal margin of the scuta.
From comparing this lower part of the carina in L. australis
(fig. 5 a), with the same part in some of the species
of the allied genus Pæcilasma, it would appear that
the fork is formed by an oblong disc, more and more
notched at the end, and with the rim between the two
points more or less folded backwards: conformably with
this view, in very young specimens of L. australis, instead
of a large and sharp fork, there is a small disc. The only
use of the fork appears to be to give firm attachment
to the membrane uniting the valves and peduncle. In
L. fascicularis, instead of a fork, there is a broad, oblong
disc (figs. 6, 6 a), rectangularly inflected; it is much longer
than the fork, in proportion to the upper part of the
carina; the disc is not more deeply embedded than the
upper part. The umbo (and primordial valve when[Pg 70]
distinguishable,) of the carina is seated just above the
embedded fork (or disc in L. fascicularis), at the point
where the inflection takes place; hence the main growth
of the carina is upwards,—the fork, however, being of
course, likewise added to at its point: in L. fascicularis,
the growth is both upwards and downwards.

Peduncle and Attachment.—The peduncle is generally
quite smooth: though with a high power its surface may
be seen to be studded with minute beads, or larger discs,
of yellowish and hard chitine; in the young of L. australis,
and I suspect of some other species, it is covered
with very minute spines. The peduncle in this genus
attains its greatest development. The cement-tissue debouches,
I believe, only through the functionless larval
antennæ, except in one species, L. fascicularis, in which a
ball of this substance is formed in a most peculiar manner
round the peduncle (Pl. I, fig. 6), apparently for the purpose
of serving as a float, as will be presently described.

Size and Colour.—The species of this genus are the
largest of the Pedunculata, with the exception of some
Pollicipes: even in the smallest species (L. pectinata),
the capitulum sometimes attains a length of about half
an inch. The peduncle varies much in length in the
same species: in L. anatifera, it is occasionally above a
foot long. The colours of L. anatifera, L. Hillii, and
L. anserifera, are very bright and striking; the membrane
bordering the valves and that round the top of peduncle
in two of the species, is of the brightest scarlet-orange;
the valves, owing to the underlying corium, are pale
blueish-grey, and the interspaces between them dark
leaden-purple. The cirri and trophi are generally dark
purple or lead-colour.

Filamentary Appendages.—These are attached to beneath
the basal articulation of first pair of cirri; they vary
in the several species, from one to five or six on each
side, the lowest being always the longest. Several of
them are occupied by testes. In L. pectinata, generally,
not even one is developed. They are subject to great[Pg 71]
variation in their proportional lengths, and in number, in
the same species. These organs have generally been considered
to serve as branchiæ; I see no reason to believe
that they are more especially designed for this end, than
is the general surface of the body.

Mouth.—The labrum is moderately bullate, the longitudinal
diameter of this part equalling about one third,
or half of that of the rest of the mouth. The palpi are
moderately developed. The mandibles (Pl. X, fig. 5)
have five teeth with the inferior point either broad, or
very narrow and tooth-like. The maxillæ are step-formed
(Pl. X, fig. 9); the first step is sometimes indistinct and
curved; and in L. pectinata, all the steps vary much, and
are more or less blended together. The outer maxillæ
(like those at Pl. X, fig. 16), are internally clothed continuously
with spines. The olfactory orifices are not at all
prominent.

Cirri.—The first pair is placed near the second pair,
and is of considerable length; the second has the anterior
ramus thicker than the posterior ramus, and the segments
brush-like; the segments (Pl. X, fig. 26) of the
four posterior cirri bear from four to six pair of long
spines, with a row of small intermediate spines: in the
posterior cirri of L. australis the lateral rim spines are
much developed; and in those of L. fascicularis, the
usual pairs of large spines are lost in a broad triangular
brush, formed by the increase of the lateral marginal, and
intermediate spines.

Caudal Appendages (Pl. X, fig. 18 b), very small, either
blunt or pointed, and quite destitute of spines.

The prosoma is well developed. The stomach is surrounded
in the upper part by a circle of large branching
cæca. The generative system is highly developed; the
testes coating the whole of the stomach, entering the filamentary
appendages and the pedicels of the cirri; the two
ovigerous lamellæ contain a vast number of ova; they are
united to rather large fræna, of which the sinuous margin
supports either a continuous row or separate tufts of glands.[Pg 72]

Distribution.—The species abound over the arctic,
temperate and tropical parts of the Atlantic, Indian and
Pacific Oceans, and are always, or nearly always, attached
to floating objects, dead or alive. The same species have
enormous ranges; in proof of which I may mention that
of the six known species, five are found nearly all over the
world, including the British coast; and the one not found
on our shores, the L. australis, apparently inhabits the
whole circumference of the southern ocean.

General Remarks and Affinities.—The first five species
form a most natural genus; they are often sufficiently difficult
to be distinguished, owing to their great variability.
The sixth species (L. fascicularis) differs to a slight
extent in many respects from the other species, and
has considerable claims to be generically separated, as
has been proposed by Mr. Gray, under the name of
Dosima; but as it is identical in structure in all the
more essential parts, I have not thought fit to separate it.
As far as external characters go, some of the species of
Pæcilasma have not stronger claims, than has L. fascicularis,
to be generically separated; and I at first retained
them altogether, but in drawing up this generic description,
I found scarcely a single observation applicable to
both halves of the genus; hence I was led to separate
Lepas and Pæcilasma. If I had retained these two genera
together, I should have had, also, to include the species
of Dichelaspis and Oxynaspis; and even Scalpellum
would have been separable only by the number of its
valves; this would obviously have been highly inconvenient.
Although some of the species of Pæcilasma so
closely resemble externally the species of Lepas, yet if we
consider their entire structure, we shall find that they are
sufficiently distinct; as indirect evidence of this, I may
remark that Conchoderma (as defined in this volume),
includes two genera of most authors, and yet certainly
comes, if judged by its whole organisation, nearer to
Lepas than does Pæcilasma.[Pg 73]

1. Lepas anatifera. Tab. I. fig. 1. (var.)

L. valvis aut lævibus aut delicate striatis: è duobus
scutis, dextro solùm dente interno umbonali instructo;
pedunculi parte superiore fuscâ.

Valves smooth, or delicately striated. Right-hand
scutum alone furnished with an internal umbonal tooth:
uppermost part of peduncle dark-coloured.

Filaments, two on each side.

Var. (a). Fig. 1. Scuta and terga with one or more
diagonal lines of dark greenish-brown, square, slightly
depressed marks.

Var. (b). (Fig. 1 b.) Carina strongly barbed.

General Appearance.—Valves white, more or less
translucent and thick, with a tinge of blueish-grey, from
the underlying corium; sometimes brownish cream-coloured,
rarely with a tint of purple. Surfaces smooth,[Pg 74]
with traces of very fine lines radiating from the umbones,
sometimes rather plain on the basal part of the scuta.
Length in proportion to the breadth of the capitulum
variable, owing to the varying degree to which the scuta
and terga have their apices produced. Scuta with the
occludent margin either considerably curved or nearly
straight. The internal tooth of the right-hand scutum,
close to the umbo, varies in size and form, being either
pointed, square, or obliquely truncated on either side, or
it has a notch on the summit; internal basal rim of the
scuta either plainly developed or nearly absent. In many
specimens (Pl. I, fig. 1), on the scuta, or on the scuta
and terga, (and sometimes more on one side of the individual
than on the other,) a nearly straight line, running
diagonally across the capitulum, of slight, quadrilateral
depressions, of a dirty greenish colour, with the edges
blending away, is either conspicuously developed, or can
only just be discerned. These marks increase in size from
the umbones to the margins of the valves. There are
sometimes two or even three rows on the scuta. They
are formed by the retention of a portion of the chitine
membrane, which is cast off the rest of the surface; the
margins of the valves are occasionally notched slightly on
the line of marks; there is no difference along this line in
the underlying corium. Specimens both with and without
a barbed carina are thus characterised. Carina; the
interspace between the carina and the scuta and terga is
not wide. The carina exteriorly, is either convex and
smooth, or furnished with knobs or with extremely sharp,
long teeth (Pl. I, fig. 1 b); small specimens, with the
capitulum under half an inch in length, are generally most
strongly barbed.[26] Apex more or less acuminated; width
and thickness variable; sides strongly furrowed. Fork
(fig. 1 a) generally less wide than the widest upper part
of the valve, with the two prongs diverging from each[Pg 75]
other at less than a right angle; their sharpness and precise
form variable; rim between them reflexed (figs. 1 a and b),
making a slight notch behind. Peduncle smooth, wrinkled,
length in proportion to that of the capitulum varying, from
barely equalling it, to six or seven times as long. I have
noticed a specimen including mature ova, with a capitulum
under half an inch long.

Filamentary Appendages;—never more than two on
each side, with sometimes only one developed; of variable
length; one seated on the flank of the prosoma, under
the first cirrus; the second close under the basal articulation
of this cirrus, on the posterior face of a slight swelling:
these appendages correspond with g and h in Fig. 4,
Pl. IX.

Mouth.—Mandibles (Pl. IX, fig. 5), with, as usual, five
teeth, all pointing downwards. Maxillæ (Pl. IX, fig. 9),
with the lower step of variable width compared to the two
upper steps. Cirri; posterior cirri with segments (fig. 26)
bearing six pair of spines; intermediate fine spines rather
long; first cirrus, anterior ramus longer by only about
two segments than the posterior ramus; second cirrus
with anterior ramus, with very broad transverse rows
of bristles; spine-bearing surfaces considerably protuberant;
caudal prominences smooth, rounded.

Size.—The largest specimen which I have seen had a
capitulum two inches in length; the longest, including
the peduncle, was sixteen inches.

Colours.—Calcareous valves already described. Edges
of the orifice bright scarlet orange; basal edges of the
scuta, and sometimes of all the valves, with a torn border
of orange membrane. Interspaces between the valves dull
orange-brown. Peduncle darkish purplish-brown, with
the lower part sometimes pale; chitine membrane itself
tinted orange; in young specimens, peduncle pale, the
colour first appearing in the uppermost part, close under
the capitulum; this upper part is often darker than the
other parts, and never orange-coloured, as in L. Hillii
and L. anserifera. Sack internally dark purplish lead-colour,[Pg 76]
sometimes with a tinge of orange, darkest under
the growing edges of the valves; body of animal pale
purplish lead-colour. The four posterior cirri blackish
purple; the second, and often the third cirrus, appear
as if the colour had been laterally abraded off; these
latter cirri have sometimes a tinge of orange. In very
young specimens, the cirri are only barred with purple.
The ova and the contents of the ovarian tubes are of a
beautiful azure blue, becoming yellow in spirits.

In museums a vast amount of difference is seen in the
colours of this species, caused by the method of preparation:
if dried without having been in spirits, and
subsequently kept dry, the orange tint round the orifice
is preserved; if kept long in spirits, this is quite lost;
but sometimes in specimens in spirits the colour of the
membrane of peduncle is preserved and rendered pinker.
The colours of the sack and animal are either quite discharged
or rendered extremely dark. The valves themselves
also often become more opaque. In some specimens
well preserved in spirits, the sack and cirri were purplish-brown
or lead-colour, tinted with dirty green, or orange,
or bright yellow, or brick-red.

General Remarks.—From the foregoing description it
will be seen how extremely variable almost every part
of this species is. I find, in the British Museum, ten
distinct specific names given by Dr. Leach to different
varieties, or rather to different specimens, for some of them
are undistinguishable. A specimen from the Sandwich
Islands, sent by Mr. Conrad to Mr. Cuming, is marked
A. engonata.

In looking over a large collection of specimens in a
museum, the most distinctive characters appear at first
to be the colours, the dentation or barbed condition of
the carina, the row of square marks on the scuta and
terga, and the more or less produced form of the whole
capitulum: all these characters are absolutely worthless
as distinctive characters, and blend into each other. In
a fresh condition, the colours of this species, and of[Pg 77]
L. anserifera and L. Hillii are surprisingly alike, though in
L. anatifera alone, the uppermost part of the peduncle is
dark. As far as I have seen, the smoothness of the
valves, together with the presence of a tooth beneath the
umbo, on the right-hand scutum, and its entire absence
on the left side, (in other species it is smaller on this,
than on the right-hand side,) is an unfailing diagnostic
mark. I believe this species is always attached to floating
objects, though there are some very young specimens
in the British Museum, collected by Sir G. Grey, adhering
to sandstone, but this may have been buoyed up by
some large sea-weed. Mr. Peach has given me the
particulars of two instances, in which, after gales of wind,
this species, of nearly full size, adhering to apparently
freshly broken-off Laminariæ, has been cast upon the coast
of England and Scotland.

2. Lepas Hillii. (Pl. I, fig. 2).

L. valvis lævibus; scutorum dentibus internis umbonalibus
nullis; carinâ à cæteris valvis, furcâ etiam a scutorum
basali margine, paululum distante; pedunculi parte
superiore aut pallidâ aut aurantiacâ.

Valves smooth; scuta destitute of internal umbonal
teeth; carina standing a little separate from the other
valves, with the fork not close to the basal margin of the
scuta; uppermost part of peduncle either pale or orange-coloured.

Filaments three on each side.[Pg 78]

General Appearance.—Capitulum laterally flat; length
varies in proportion to the breadth; valves white, somewhat
translucent, moderately thick, very smooth, but with faint
traces of radiating lines; in some varieties, surface rather
irregular along the zones of growth. Scuta without any
internal teeth, and with scarcely any trace of the internal
basal rim; upper angle little acuminated; the occludent
margins of the two scuta stand rather separate from each
other, showing a wide space of corium between them: these
margins are arched and protuberant, but with the lower
part a little hollowed out; basal margin a little curved.
In one specimen alone, I saw a trace of a diagonal line of
square coloured marks, like those common in L. anatifera.
Terga rather broad, with the basal angle not much
acuminated. The degree of prominence and outline of
the double occludent margin varies very much. Carina,
separated by a rather wide space from the scuta and
terga; of very varying shape, the upper part not much
acuminated, generally very flat, sometimes exteriorly
marked by a central depressed line; never barbed;
occasionally, (in a specimen from Australia,) middle part
so wide as almost to become spoon-shaped; on the other
hand occasionally of nearly the same width throughout;
somewhat constricted above the fork. Fork deeply
embedded as usual; situated, in fresh specimens, a little
way beneath the basal margins of the scuta, instead
of touching them, as in the other species; forks of varying
width, not so abruptly inflected as in many species;
sometimes much narrower than the upper widest part of
the valve, sometimes nearly twice as wide; prongs of fork
not very sharp, diverging at about a right angle, with the
rim between them reflexed. The apex of the carina
extends up between the terga for barely half their length,[Pg 79]
instead of up fully three fourths of their length, as in
L. anatifera.

The chitine membrane at the base of the capitulum,
especially at the anterior and posterior ends, is covered
with beautiful, little, embedded, yellowish beads, about
3/2000th of an inch in diameter; above this, on each side of
the carina, there is a space with similar but smaller little
spheres, and still higher up still minuter ones; others
occur on different parts of the capitulum; these spaces
are seen to be distinctly separated from each other, and
present a beautiful appearance under a high power.

Peduncle, as long as, or rather longer than, the capitulum:
in one set of specimens, however, it was thrice or
four times as long as the capitulum. The peduncle, in
some specimens, was conspicuously covered with transverse
plates of yellowish hard chitine.

Filamentary Appendages.—Three on each side; one on
the flank of the prosoma, with a pair beneath the basal
articulation of the first cirrus; relative lengths various,
but the posterior filament of the pair under the cirrus, is
the shortest. Mouth; palpi not much acuminated;
maxillæ step-formed, but with the upper or first step in
some specimens indistinct, or forming a curve. Cirri;
the segments of the first cirrus and of the posterior arm
of the second cirrus are highly protuberant, the protuberances
sometimes equalling half the thickness of the segments
themselves. Caudal appendages smooth, rounded.

Size.—The largest specimen which I have seen, in
the collection of Mr. Cuming, had a capitulum 1-1/10th of
an inch long, and 1-1/4 wide; therefore not quite equalling
in size the largest specimens of L. anatifera.

Colours.—When fresh, valves blueish-grey from the
underlying corium, edges of all the valves and round the
orifice, and round the top of the peduncle, bright orange-yellow,
passing into the finest scarlet, and varying
slightly in tint in different specimens. Space between the
carina and the other valves, and between the occludent
margins of the scuta, rich purplish-brown; peduncle[Pg 80]
either pale or purplish-brown, or only clouded on the
sides with the same. In young specimens, peduncle
nearly colourless; and in those under a quarter of an inch
long in the capitulum, the top of the peduncle has not
acquired its orange tint. Sack pale, leaden-purple, body
the same, but paler and more reddish; cirri (but only
the tips of first pair) tinted with fine golden orange.
Immature ova in peduncle beautiful blue. After being
long kept in spirits, the colours are changed, weakened,
or discharged, as in L. anatifera and L. anserifera,
and the valves become opaque. In some long-kept specimens
the corium everywhere had become pale brown;
more usually it assumes a dirty purplish lead-colour.

Monstrous Variety.—Amongst a set of ordinary specimens
from a ship from Genoa, sent me by Mr. Stutchbury,
there were three, one full-grown and two very young,
with the whole capitulum, (and likewise with the scuta
and terga taken separately,) not above half the usual
length in proportion to the breadth. Neither the colours
nor animal in this variety presented any difference.

General Remarks.—This species is almost universally
confounded with L. anatifera. Quoy and Gaimard, however,
appear to have distinguished it, under the name of
A. tricolor, from its colours. Leach named it accidentally,
for he specifies not one distinctive character,
and besides his two published names, he has appended
two other names to specimens in the British Museum.
A specimen, from the Sandwich Islands, sent by Mr.
Conrad to Mr. Cuming, is marked A. substriata. In a
dry state, from the shrinking of the membranes, and
consequent approach of the carina to the other valves,
and of the fork to the basal margin of the scuta, it is
most difficult to distinguish this species, though so
decidedly distinct, from L. anatifera; the absence, however,
of a tooth on the under side of the right-hand
scutum is at once characteristic. Even in specimens
kept in spirits, in which there has been no shrinking,
but in which the colours have changed, and taking into[Pg 81]
account the variation in the carina and upper part of the
terga, this species is not always readily distinguished
from L. anatifera, without opening the valves and looking
for the right-hand tooth of the latter. In fresh specimens,
the orange ring at the top of the peduncle, and the broad
purplish interspace between the carina and other valves,
are characteristic. In all states, the filamentary appendages
offer a good character.

3. Lepas anserifera. Pl. I, fig. 4.

L. valvis approximatis leviter sulcatis (tergis præcipuè);
scuto dextro dente forti interno umbonali, lævo aut dente
exiguo, aut merâ cristâ instructo; margine occludente
arcuato, prominente: pedunculi parte superiore aurantiacâ.

Valves approximate, slightly furrowed, especially the
terga; right-hand scutum with a strong internal umbonal
tooth; left-hand with a small tooth, or mere ridge;
occludent margin arched, protuberant: uppermost part of
peduncle orange-coloured.[Pg 82]

Filaments five or six on each side.

Var. (dilatata, young); valves rather thin, finely furrowed,
often strongly pectinated; scuta broad, with the
occludent margins much arched, making the space wide
between this margin and the ridge connecting the umbo
and the apex: carina often barbed.

General Appearance.—Capitulum more or less elongated
relatively to its breadth; in two specimens, with
scuta of equal width, one was longer than the other by
the whole of the occludent margin of the terga. Valves
white, thick, (in young specimens sometimes diaphanous
and thin,) closely approximate to each other; surfaces
furrowed to a very variable amount. Terga generally
more plainly furrowed than the scuta, of which the basal
portion is generally less furrowed than the upper part;
ridges, often rough, generally much narrower than the
furrows: in half-grown specimens (var., dilatata of
Leach,) the ridges are frequently denticulated, and there
is even sometimes a row of bead-like teeth along the
basal margins of the scuta. The ridges vary much,
sometimes alternately wide and narrow; in two specimens
of equal size, there were, in one, thirty-two ridges,
and in the other only eighteen, on the scutum.

Scuta, with the occludent margin rounded and protuberant
to a variable degree, but always leaving a
rather wide space between the margin, and the ridge
which runs from the umbo to the apex; apex pointed.
Right-hand internal tooth considerably larger than that
on the left, which is often reduced to a mere ridge;
internal basal rim thick, sometimes furrowed along its
upper edge, but of variable thickness, sometimes not
extending as far as the baso-carinal angle. Terga, sometimes[Pg 83]
equalling, sometimes only two-thirds of, the length
of the scuta; in young specimens, the two occludent
margins form a right-angle with each other; in older
specimens they form less than a right-angle, and hence
the portion of valve thus bounded is unusually protuberant.
Carina, within deeply concave; exterior sides finely
furrowed longitudinally, generally denticulated; valve only
slightly narrowed in above the fork, of which the prongs
diverge at an angle of 90°, or rather more, and are wider
than the widest upper part of the valve; rim between the
prongs reflexed; the heel or external angle, just above
the fork, sometimes considerably prominent. I have seen
only a single large specimen with its carina barbed.
In half-grown specimens, (var. dilatata, Leach,) the carina
is often strongly barbed, with the upper point much acuminated,
the fork about twice as wide as the widest upper part,
and the prongs diverging at rather more than a right-angle.
In some specimens, especially very young ones, there are
at the base of the carina, above the fork, some strong,
downward-pointed, inwardly-hooked, calcareous teeth;
such occur also in some specimens along the basal margins
of the scuta, two of these hooked teeth under the umbones
of the scuta being larger than the rest: specimens
conspicuously thus characterised came from the Navigator
Islands; in these, I may add, the acutely triangular primordial
valves were quite plain.

Peduncle, generally about as long as the capitulum; in
young specimens generally short.

Filamentary Appendages, generally five, sometimes six,
on each side; one is seated on the side of the prosoma,
and the four others placed in pairs beneath the basal
articulation of the first cirrus; the lowest posterior
filament of the four generally is the largest. In young
specimens, having a capitulum only half an inch long,
the upper pair of the four often is not developed, or
is represented by mere knobs. The mouth presents
no distinctive characters. Cirri, with the longer ramus
of the first pair almost equal to the shorter arms of the[Pg 84]
second pair; spine-bearing surfaces only slightly protuberant.
Caudal appendages smooth, curved, pointed.

Size.—The largest specimen which I have seen, had a
capitulum one inch and a half in length.

Colours.—The white valves are edged with bright
orange membrane; and are so close to each other that
no interspaces, coloured from the underlying corium, are
left. Peduncle, dark orange-brown, with the uppermost
part under the capitulum bright orange all round; the
chitine membrane itself being thus coloured. Sack, internally,
dark purplish lead-colour. Body and cirri,
either nearly white or pale purplish-lead colour, with the
arms of the second, third, and fourth cirri, and pedicels of
the fifth and sixth, more or less tinted with orange. A
specimen preserved during fourteen months in good spirits
had only a tinge of orange left round the orifice and round
the upper part of peduncle, and on the cirri. In some
other specimens, badly preserved, the chitine membrane
was quite colourless, and sack and cirri dirty lead-colour.
Fresh ova, peach-blossom-red; immature ova, in ovarian
tubes, pale pink.

Monstrous Variety.—In Mr. Stutchbury’s collection,
there was a specimen, with the scuta, broad, smooth, thin,
and fragile, without any ridge running from the umbo
to the apex, and with the occludent margin reflexed.
This seemed caused by the shell having been attacked by
some boring animal, and from having supported Balani.
In the same specimen the first cirrus on one side was
monstrously thick and curled; the second cirrus had its
posterior ramus in a rudimentary condition. In Mr.
Cuming’s Collection, there are small specimens with
the zones of growth overlapping each other, with thick
irregular margins, and with the carina distorted.

This species has cost me much trouble: I have
examined vast numbers of specimens, from a tenth to
half an inch in length, attached to light floating objects,
such as Janthinæ and Spirulæ from the tropical oceans,
which all resembled each other, and slightly differed[Pg 85]
from the common appearance of L. anserifera: this
variety is the Pentalasmis dilatata of Leach; and for
a long time I considered it as a distinct species. It
differs from L. anserifera, in the less thickness of the
valves, in their being more finely and yet plainly furrowed;
in the greater width of the scuta; and more
especially, of that part of the valve lying between the
occludent margin, and the ridge running from the
umbo to the apex; in the less elongation of the area in
the terga, bounded by the two occludent margins; and,
lastly, in the less size of the whole individual. The
trophi and cirri are absolutely identical. Lately, however,
in carefully going over a great suite of specimens,
all the above few distinctive characters broke down and
insensibly graduated away; and I am convinced that this
form is only a variety of L. anserifera; its different aspect
being caused partly by youth, but chiefly, I suspect, from
being attached to light objects floating close to the surface
of the sea.

The Lepas anserifera can be distinguished by the
slight furrows on its valves from all the other species,
excepting L. pectinata: this latter species can be
readily known, by the close proximity in the scuta
of the occludent margin, and the ridge extending from
the umbo to the apex; by its carina being very narrow
above the fork; by the prongs of the fork diverging
at an angle of from 135° to 180°; by the thinness of
its valves; by the coarseness of the furrows on them;
and lastly, by there being at most in L. pectinata only
one filamentary appendage beneath the first cirrus.

4. Lepas pectinata. Pl. I, fig. 3.

L. valvis tenuibus, crassè sulcatis, sæpe pectinatis; scutorum
cristâ prominente ab umbone ad apicem juxta marginem
occludentem pertinente: furcæ carinalis cruribus
inter angulos 135° et 180° divergentibus.

Valves thin, coarsely furrowed, often pectinated. Scuta
with a prominent ridge extending, from the umbo to the
apex, close to the occludent margin; fork of the carina
with the prongs diverging at an angle of from 135° to
180°.

Filaments absent, or only one on each side.

Var. (Pl. I, fig. 3 a), upper part of the terga (bounded
by the two occludent margins) produced and sharp;
surface of all the valves often coarsely pectinated, and
with the carina barbed.

General Appearance.—The capitulum varies considerably
in length compared to its breadth, caused chiefly by
the greater or less production of the occludent portion of
the terga; valves thin, brittle; the furrowed surface varies[Pg 87]
much in character, narrow and broad ridges often alternating;
frequently each ridge (but more especially the
ridge running from the umbo to the apex of each scutum,
and sometimes that alone,) is covered with prominent,
curled, flat, calcareous spines, giving the shell an appearance
like that of many mollusca. Other specimens show
no trace of these calcified projections. From the thinness
of the valves and the depth of the furrows, the margins
of the valves are sinuous. Scuta: the ridge running
from the umbo to the apex is unusually prominent and
curved; it runs very close to the occludent margin, so
that, differently from in all the other species, only a very
narrow space is left between this margin and the ridge.
Internal teeth, under the umbones, either sharp and prominent,
or mere knobs; sometimes that on the right side
is much larger than that on the left; sometimes they are
nearly equal; sometimes that on the left is scarcely distinguishable.
Internal basal rim absent, or barely developed.

Terga: these valves have a conspicuous notch to receive
the apex of the scuta; the two occludent margins either
meet each other at a rectangle, or at a much smaller angle,
causing the portion thus bounded to vary much in outline,
area, and degree of prominence. This at first led
me to think that the P. spirulæ of Leach, in which the
point is very sharp and prominent, was a distinct species;
but there are so many intermediate forms, that the idea
must be given up. I may remark, that in all the species
of Lepas, the upper part of the tergum seems particularly
variable. The degree of acumination of the basal portion
of the tergum also varies; the internal surface sometimes
has small crests radiating from the umbo.

Carina, broad, within deeply concave; edges sinuous,
externally sometimes strongly barbed; narrow above the
fork, which latter is wider than the widest upper part of
the valve; prongs sharp, thin, diverging at an angle of
from 135° to 180°; the rim connecting the prongs not,
or only slightly, reflexed.

Peduncle, narrow, shorter than the capitulum.[Pg 88]

Filamentary Appendages, none, or only one, short,
obtuse projection on each side, on the posterior face of
the swelling under the first cirrus.

Mouth.—Mandibles, with the inferior point produced
into a single pectinated tooth, rarely into two pectinated
teeth; on one side of one specimen, there were only four
instead of five teeth. Palpi very narrow. Maxillæ highly
variable; they may be described as formed of five steps,
of which the two lower ones are generally united into a
single one, divided by a mere trace of a notch; or with the
three lower steps blended into an irregular, projecting
surface, and with even the fourth step indistinct. I have
seen these two extreme forms on opposite sides of the
mouth of the same individual,—on one side the maxillæ
being regularly step-form, on the other the whole inferior
part forming an almost straight edge, standing high up
above the first notch or step which bears the two upper
great spines.

Cirri.—First pair rather far removed from the second
pair, with the longer ramus about three-fourths of the
length of shorter ramus of second cirrus; spine-bearing
surfaces, hardly at all protuberant; lateral marginal spines
on the posterior cirri rather long; caudal appendages
smooth, rounded, extremely minute: penis very spinose.

Size.—Capitulum in the largest specimen, six-tenths of
an inch long; only a few arrive at this size.

Colours, after having been kept in spirits,—sack and
cirri, especially first cirrus, clouded with pale purple;
peduncle brownish; valves appear blueish in specimens
not long preserved, but in specimens kept longer they
become perfectly and delicately white.

General Remarks.—Under the head of L. anserifera, I
have made some remarks on the diagnostic characters of
this species. In the thinness of the valves,—form of the
carina, with the rim connecting the prongs being not, or
scarcely, reflexed,—and in the shortness and narrowness
of the peduncle, there is some approach to L. australis,
and thence to L. fascicularis. In the form of the maxillæ,—in[Pg 89]
one specimen having the mandible on one side
bearing only four teeth,—and in the frequent absence of
filamentary appendages, there is some approach to the
genus Pæcilasma; but there is no such approach in the
characters derived from the capitulum. We have seen
that, as in so many other species of this genus, most
of the parts are variable, and this is the case to a most
unusual extent in the form of the maxillæ. Dr. Leach
has attached eight specific names to the specimens
preserved in the British Museum.

5. Lepas australis. Pl. I, fig. 5.

L. valvis glabris, tenuibus, fragilibus; scutorum dentibus
umbonalibus utrinque internis; carinæ parte superiore
latâ, planâ, suprâ furcam valdè constrictâ; furcæ cruribus
latis, planis, tenuibus, acuminatis, intermedio margine
non relexo.

Valves smooth, thin, brittle; scuta with internal umbonal
teeth on both sides. Carina with the upper part
broad, flat; much constricted above the fork, which has
wide, flat, thin, pointed prongs, with the intermediate
rim not reflexed.

Filaments, two on each side.

General Appearance.—Capitulum rather obtuse and
thick; valves thin, brittle, approximate, either white
and transparent, or dirty-brown and opaque; or sometimes
tinted internally with purple (perhaps the effects of
being preserved in spirits); surface plainly marked by
lines of growth, rarely marked with traces of lines radiating
from the umbones. Scuta with teeth on both sides,[Pg 90]
nearly equal; internal basal rim rather wide, sometimes
furrowed; basal margin considerably curved inwards.
Terga rather wide; basal angle blunt; angle formed by
the two occludent margins blunt and rounded. Carina
(fig. 5 a) with the apex blunt, flat; the middle part generally
very broad; much constricted above the fork, where
it is internally deeply concave, and externally carinated;
fork twice as broad as the broadest upper part of the
valve; with the prongs flat, broad, thin, pointed, diverging
at about an angle of 75°, with the intermediate rim not
at all reflexed; the fork generally not deeply imbedded in
the chitine membrane of the peduncle, so as to be quite
easily visible externally; sometimes there is an internal,
transverse, depressed line on the fork. In young specimens,
with the capitulum about a quarter of an inch long, the
fork of the carina is not developed, the lower slightly inflected
portion consisting simply of an oval plate, twice
as wide as the upper part. Until I had carefully examined
a perfect series, showing the gradual changes in
this part, I did not doubt that the young specimens formed
a distinct species, and named it accordingly: the shortness
of the penis first made me perceive that the specimens
were immature. At this early age, I may add, the filamentary
appendages were not developed. Peduncle either
quite short, or as long as the capitulum, close under which
it is considerably constricted all round.

Filamentary Appendages.—Two on each side; one long,
tapering, placed on the prosoma (in one specimen represented
by a mere knob), and the second shorter, situated
on the posterior margin of the swelling beneath the first
cirrus.

Mouth.—Maxillæ, with three large spines at the
upper angle, and with the first step distinct, but narrow;
mandibles with five teeth; in young specimens the inferior
point ends in a single spine; sides of the supra-oral
cavity very hairy; the membrane, forming the inner fold
of the labrum, yellow and thickened in the form of a spoon.

Cirri.—In the posterior cirri there are, at the upper[Pg 91]
lateral edges of the segments on both sides, small spines;
the segments in the first cirrus, and in the broad anterior
ramus of the second cirrus, are hemispherically and considerably
protuberant. Caudal appendages smooth.

Size.—The largest specimen had a capitulum one inch
long.

The Colours (after having been long in spirit) of the
valves have already been given; sack and peduncle dirty
yellowish-brown, with the parts corresponding to the margins
of the valves much darker brown, or almost black; segments
of the cirri clouded with dark brown; body and pedicels
of the cirri dirty yellowish. I have reason to believe
that the colours are totally different in living specimens.

Monstrous Varieties.—Most of the specimens from lat.
50° S., on the coast of Patagonia, were more or less
deformed, with the successive zones of growth overlapping
each other, and forming coarse concentric ridges. The
carina in several specimens was laterally distorted.

I have already remarked that this species has some
affinity to L. pectinata; but it is much more closely related
to L. fascicularis, the affinity being clearly shown
by the thinness and translucency of the valves, their convexity,
by the width and little acumination of the upper
part of the carina, by the width of the fork, and by its not
being deeply imbedded. In young specimens, moreover,
before the fork is fully developed, there is a remarkable
similarity between the two species, in the form of this
lower part of the carina. Again, the narrowness and
inflection of the peduncle under the capitulum in L. australis,
and lastly, the lateral marginal spines on both sides
of the segments of the posterior cirri, all clearly indicate
this same affinity to L. fascicularis.

I believe this species is confined to the southern ocean;
and perhaps there represents L. fascicularis of the northern
and tropical seas. It must, judging from the number
of specimens brought home by Captain Sir J. Ross, and
from those previously in the British Museum, and from
those collected by myself, be a very common species.[Pg 92]

6. Lepas fascicularis. Pl. I, fig. 6.

L. valvis glabris, tenuibus, pellucidis; carinâ rectangulè
flexâ, parte inferiore in discum planum oblongum expansâ.

Valves smooth, thin, transparent; carina rectangularly
bent, with the lower part expanded into a flat oblong
disc.

Filaments, five on each side; segments of the three
posterior cirri with triangular brushes of spines.

Var. (Donovani, of Leach.) Carina with the upper
part flat, spear-shaped, externally with a narrow central
ridge.

Var. (Villosa. Pl. I, figs. 6 b, c.) Valves placed rather
distant from each other; carina extremely narrow, with
the upper part of nearly the same width throughout;
terga with the lower part much acuminated; body of
animal finely villose.

General Appearance.—Capitulum highly variable in
all its characters; thick and broad in proportion to its
length, but the breadth is variable,—in some specimens,
the capitulum being longer by one-fifth of its total length
than broad; in others, one-fifth broader than long. Valves
generally approximate; in some varieties, however, from
the narrowness of the carina and terga, the valves stand
far apart, there being an interval between the carina
and scuta of nearly half the breadth of the latter. Valves
excessively thin, brittle, transparent, colourless, smooth,
but generally sinuous along the zones of growth, which are
conspicuous: valves generally covered throughout by thin
chitine membrane, which is thickly clothed, especially in
the interspaces between the valves, with minute spines,
barely visible to the naked eye. Scuta with the lower
part of the tergo-carinal margin extremely protuberant;
occludent margin, more or less, but slightly reflexed,
with a depressed line running from the umbo to the
apex; basal margin much reflexed, but to a variable
extent and at a varying angle, even up to a right angle,—an
external rim or collar being thus formed. There
are no distinct internal teeth, but the basal margin
under the umbones, is more or less distinctly produced
into a rounded disc or projection, which is generally
not so much outwardly reflexed as the rest of the basal
margin: there is no distinct internal basal rim. The
primordial valves are generally visible, but they do not
lie, as in all other species, close to the basal margin, but
a little above it,—the lower reflexed portion having been
subsequently developed. Terga flat, with the occludent
margin slightly arched, and not, as in the foregoing species,
formed of two sides; apex bent towards the carina;
width of the lower half highly variable, owing to the
varying extent to which the scutal margin is hollowed[Pg 94]
out; in some specimens, the whole lower half beneath the
apex of the scuta is of nearly the same width throughout;
in other specimens this lower part is spear-shaped. The
widest part of the tergum either equals in width, or is only
two-thirds of the width of the widest part of the carina
beneath its umbo. Carina (Pl. I, fig. 6 a) highly variable
in shape, with the part above the umbo either spear-shaped
and slightly concave within, or nearly flat and
furnished with a central external ridge; or the upper
part (fig. 6 c) is of equal and extreme narrowness throughout,
and deeply concave within, appearing as if only the
central ridge had been developed. The part below the
umbo, (answering to the fork in the foregoing species,)
is about one-third of the length of the whole valve, and
generally twice as wide as the upper part, but in the
variety with the upper part of the carina equally narrow
throughout, the lower part is thrice as wide as the upper;
the disc, or lower part, is generally slightly concave
within, exteriorly either with or without a central ridge;
basal margin rounded; lateral margin more or less
curved, according to the form of the upper part. The
disc is not more deeply imbedded in membrane than is
the upper part of the valve. The heel or umbo is either
angular and prominent, or rounded. In very young
specimens the carina is simply bowed, instead of being
rectangularly bent.

Peduncle,—short, narrow, being abruptly inflected all
round under the basal edges of the capitulum; lower part
of very variable shape, being often suddenly contracted
into a mere thread (fig. 6 b), which sometimes widens
again at the extreme end. The external membrane is
very thin, and is penetrated by the usual fine tubuli
leading to the corium; its surface is wrinkled and destitute
of spines, or with extremely few. The peduncle is
often completely surrounded by a yellowish ball, (of
which I have seen specimens from the coast of England,
and from off Borneo,) sometimes half as wide as the
capitulum, composed of very tender, vesicular, structureless[Pg 95]
membrane, and of a pulpy substance: perhaps the
yellow colour may be owing to long immersion in spirits.
Some authors have supposed that the ball was the ovisac
of the animal; and for the first few minutes, deceived by
the numerous included spores of, as I believe, Bacillariæ,
I thought that this was the case; others have supposed
that it consisted of some encrusting algæ or other foreign
organism; but it is, in reality, a most singular development
of the cement-tissue, which ordinarily serves
to attach Cirripedes by their bases to some extraneous
object, but here surrounding that object and the peduncle,
gives buoyancy, by its vesicular structure, to the
whole. The membrane of the ball falls to pieces in
caustic potash, differently from the chitine membrane of
the enclosed peduncle, and this shows that there is some
difference in composition from ordinary cement. The
ball, when cut in two, exhibits an obscure concentric
structure. The whole is excreted by the two cement-ducts,
through two rows of orifices, one on each side of
the surrounded portion of the peduncle; and I actually
traced, in one case, the yellow pulpy substance coming
out of the cement-ducts. The upper apertures are in
gradation larger than those below them, and they stand
a little further apart from each other; these are figured
as seen from the outside, much magnified, at Pl. I,
fig. 6 d. I did not succeed in finding the cement-glands,
but I followed the ducts, of rather large size, running
for a considerable distance as usual along and within the
longitudinal muscles of the peduncle. Nearly opposite
the uppermost aperture, on each side, the duct passes
out through the corium, and becomes laterally attached
to the outer membrane of the peduncle, at which point
an aperture is formed (as in other cases, by some unknown
process), thus giving exit to the contents of the
duct. Beneath this upper aperture the duct runs down
the peduncle, between the corium and the outer membrane,
till it comes to the next aperture, to which it is
also attached, and so on to all the lower ones; but I[Pg 96]
believe no cement tissue continues to pass out through these
lower apertures. Beneath the lowest aperture the two
ducts run into the two prehensile antennæ of the larva,
which, as usual, terminate the peduncle. The antennæ are
attached to some small foreign body in the centre of the
vesicular ball, by the usual tough, light brown, transparent
cement. The two upper apertures are nearly on a
level with the outside surface of the ball; and it was
evident that as the animal grows, new apertures are
formed higher and higher up on the sides of the peduncle,
and that out of these, fresh vesicular membrane proceeds,
and grows over the old ball in a continuous layer.
It appears that the growth of the vesicular ball is not
regular,—that it is not always formed,—and that when
formed the whole, or the lower part, sometimes disintegrates
and is washed away. As that portion of the
peduncle which is enclosed ceases to grow, and has its
muscles absorbed, retaining only the underlying corium,
whereas the upper unenclosed portion, and likewise, (as it
appears) lower portions once enclosed but since denuded,
continue to increase in diameter, the peduncle, when the
vesicular ball is removed, often has the most irregular
outline, contracting suddenly into a mere thread, and
then occasionally expanding again at the basal point.

Frequently two or three specimens have their peduncles
imbedded in one common ball, of which there is a fine
specimen in the College of Surgeons (Pl. I, fig. 6), the
ball being about one inch and a quarter in diameter,
with a slice cut off. In this specimen, it is seen that the
vesicular membrane proceeding from several individuals,
unites to form one more or less symmetrical whole, and
that the original common object of attachment is entirely
hidden. Dr. Coates[29] gives a curious account of the infinite
number of specimens, through which he sailed during
several days, in the Southern Atlantic Ocean: the balls
appeared like bird’s eggs, and were mistaken for some[Pg 97]
fucus, which was supposed to have encrusted the scales of
the Velellæ, to which the Cirripede had originally become
attached. Several individuals had their peduncles imbedded
in the same ball, “which floated like a cork on
the water.” As this species grows into an unusually
bulky animal, we here see a beautiful and unique contrivance,
in the cement forming a vesicular membranous
mass, serving as a buoy to float the individuals, which,
when young and light, were supported on the small
objects to which they originally had been cemented in
the usual manner.

Filamentary Appendages.—Five on each side, of which
four lie in pairs at the base of the first cirrus (of these,
only three are sometimes developed), and one on the
flank of the prosoma.

Mouth.—Palpi much acuminated. Mandibles with five
teeth; the first not far remote from the second; inferior
point rather broad and finely pectinated. Maxillæ with
two large, unequal, upper spines, and four regular steps.

Cirri.—Posterior cirri, with the upper parts of the
segments slightly protuberant; in young specimens, the
spines can be seen to consist of five pairs, placed in two
converging lines in the upper half of each segment, with
numerous minute, latero-marginal, and intermediate little
bristles: in large specimens, all these latter have so increased
in number, that the normal five pair cannot be
distinguished, and the front of each segment is covered
by a triangular thick brush of bristles, all pointing in the
same direction, thus giving a very unusual character to
the posterior cirri: the dorsal tuft on each segment consists
of six or seven large spines, with from one to three
dozen fine ones. First cirrus and anterior ramus of second
cirrus with broad brushes of bristles. The pedicels of
all the cirri are thickly covered with bristles. Caudal
appendages smooth, with rounded summits.

Penis very hairy: vesiculæ seminales purple, much
convoluted, lying within the prosoma; testes dendritic,
scarcely enlarged at their terminal points, purplish;[Pg 98]
ovigerous fræna large with sinuous margins, the glandular
beads being arranged in groups.

Size.—The largest specimen (from the coast of Devonshire)
had a capitulum 1.6 of an inch long, and 1.2
broad, and of unusual thickness.

Colours, after having been in spirits: front surfaces of
the segments of the cirri and of the pedicels purple.
In some specimens from off Borneo, parts of the sack
and the interspaces between the two scuta, were of a fine
purple. Montagu states, that the whole shell and body
of animal, when fresh, are pale blue, with the cirri spotted
with brown.

General Remarks.—The extreme variability of this
species is remarkable. In the College of Surgeons, there
is a group of specimens collected by Mr. Bennett, I
believe, in the Atlantic, in which the extreme narrowness
of the carina and of the terga (Pl. I, fig. 6, b, c)
(with consequent wide spaces of membrane left between
these valves), led me, at first, to entertain no doubt, that
it was quite a distinct species, which was strengthened
by finding that the whole surface of the cirri were villose,
with very minute spines; hence I called this variety,
villosa. On the closest examination, however, I could
detect no other differences, and the narrowness of the
carina and terga varied very considerably: moreover, in
one of the specimens, which was about intermediate in
the form of its valves between this variety and the common
form, the surfaces of the cirri were not in the least
degree villose. Again, in some other specimens, the
terga were as narrow as in Mr. Bennett’s, whilst the
carina had its usual outline.

In a var. (called by Leach, P. Donovani,) from the
Atlantic, under the Equator, the carina is remarkable from
the extreme flatness of the upper part, and from the presence
of an exterior, narrow, central ridge. In one
specimen from Jersey, in the British Museum, the carina
made an extremely near approach to this same form.

Affinities.—This species is certainly much the most[Pg 99]
distinct of any in the genus, and Mr. Gray has proposed
to separate it under the name of Dosima; but considering
the close similarity of the whole organisation of the
internal parts, together with the transitional characters
afforded by L. australis, I think the grounds for this
separation are not quite sufficient. I have remarked,
under L. australis, on the affinity between that and
the present species. In the carina terminating in a disc
(though here not imbedded), there is some slight affinity
to Pæcilasma eburnea and crassa, and markedly so in the
arrangement of the bristles on the posterior cirri. In
the valves being covered with villose membrane, and to a
certain extent in the form of the carina and of the occludent
margin of the terga, and especially in the two rows
of cement-orifices in the peduncle, there is some affinity
to Scalpellum.

Pæcilasma. Nov. Genus.[30] Plate II.

Valvæ, 3, 5, aut 7, approximatæ: carina solùm ad
basales apices tergorum extensa, termino basali aut
truncato aut in discum profunde infossum producto:
scuta pænè ovalia, umbonibus ad angulum rostralem
positis.

Valves, 3, 5, or 7, approximate: carina extending only
to the basal points of the terga; with its lower end
either truncated or produced into a deeply imbedded
disc. Scuta nearly oval, with their umbones at the
rostral angle.

Mandibles with four teeth; maxillæ notched, with the
lower part of edge prominent; anterior ramus of the[Pg 100]
second cirrus not thicker than the posterior ramus;
caudal appendages uniarticulate, spinose.

I have already given my reasons for instituting and
separating this genus from Lepas; as far as the capitulum
is concerned, the differences between these genera
certainly appear trivial; they consist in the carina not
extending up between the terga, and in the lower end
being either truncated, or produced into an imbedded
disc: the terga have a single occludent margin. The
included animal’s body differs in more important respects;
for both mandibles and maxillæ are very distinct;
the cirri of some of the species also differ; and
the caudal appendages are here always spinose: there
are no filamentary appendages: and lastly, the habits are
different.

The genus may be divided into two sections, firstly,
P. Kæmpferi and P. aurantia, which have their carinæ
basally truncated, the basal angles of their terga cut
off, and the anterior rami of their second cirri shorter
than the posterior rami; and, secondly, P. crassa, P. fissa,
and P. eburnea, which in these several respects are otherwise
characterised. The P. eburnea, however, differs
rather more from P. crassa and P. fissa, than these two
do from each other; but certainly not enough to allow of
the retention of Mr. Hinds’ genus of Trilasmis. P. crassa,
in an especial degree, connects together all the forms.

General Appearance.—Capitulum oval, more or less
produced, flat or gibbous; formed of three, five, or seven
approximate valves; the lesser number arising from the
abortion of the terga, and the greater number from the
scuta being divided into two segments. Valves moderately
thick, either white or reddish, smooth or striated,
and sometimes partly covered by membrane, bearing
minute spines. Scuta oval, of varying proportions; the
basal margin is generally narrow, and blends into the[Pg 101]
carina-tergal margin; the internal basal rim generally is
well developed, sometimes with, and sometimes without
internal teeth beneath the umbones. In P. eburnea, and
sometimes in P. crassa, there is a line of apparent fissure,
and in P. fissa of actual disseverment, running from the
umbo to the apex of each scutum, nearly in the line in
which a ridge extends in Lepas: the primordial valves
of the scuta in these three species, are seated at the
basal angles of the lateral and larger segments. The
positions of the primordial valves, and the direction of
growth in the calcified valves, are, in all the species, the
same as in Lepas. In several of the species attached to
Crustacea, the two scuta are unequally convex, which is
caused, as was pointed out to me by Mr. Gray, by that
valve which lies close and nearly parallel to the body of
the crab, being least developed. The Terga are either
quite absent, or rudimentary as in P. crassa, or pretty
well developed as in the other species: the occludent
margin is single, and not double as generally in Lepas;
the basal angle is either pointed or truncated. The Carina
varies considerably in shape, but never extends up between
the terga, nor ends downwards in a fork; in the first
two species it is truncated; in the others, it terminates
in a deeply-imbedded oblong disc, which in P. eburnea
seems almost entirely (but of course not quite) to separate
the inside of the capitulum from the peduncle;
a similar separation is effected in P. fissa, where the
imbedded disc is small, by two large teeth on the
internal basal rims of the two scuta. The carina is
always narrow, and either solid internally or very slightly
concave.

Peduncle, is very short and narrow; the membrane is
generally ringed with thicker, yellower portions, and often
bears very minute spines.

Size.—All the species are small, with a capitulum not
exceeding half an inch in length.

Filamentary Appendages.—None.

Mouth.—Labrum generally considerably bullate in[Pg 102]
the upper part, with a row of teeth on the crest. The
mandibles have four teeth, with the inferior point narrow
and spine-like, or rudimentary and absent. The maxillæ
have, under the two or three upper great spines, a deep
notch itself bearing spines; beneath this, the lower part
is straight and considerably prominent, Pl. X, fig. 15.
Outer maxillæ are covered on their inner sides continuously
with spines.

Cirri.—The first pair is sometimes seated very distant
from the second. The arrangement of the spines on the
posterior cirri varies, to an unusual degree within the
limits of the same genus. We have either the ordinary
structure of anterior pairs, with single fine intermediate
spines (as in P. Kæmpferi and aurantia), or we have the
pairs increased by one or two additional longitudinal
lateral rows, as in P. eburnea; or we have the front
spines forming a single transverse row, as in P. crassa
and P. fissa, Pl. X, fig. 29, a. The segments in none
of the species are protuberant; the anterior ramus of
the second cirrus does not seem to be thicker than the
posterior ramus, as is usually the case. The rami of the
second, and of most of the other cirri, are unequal in
length,—the anterior ramus, contrary to the ordinary
rule, being longer in P. eburnea, P. fissa, and P. crassa,
than the posterior ramus by several segments; I have
hitherto observed this inequality only in the sessile genus
Chthamalus.

The Caudal Appendages are small, uniarticulate, and
always furnished with bristles.

1. Pæcilasma Kæmpferi. Pl. II, Fig. 1.

P. valvis 5; carinæ basi truncatâ et cristatâ: scutorum
dentibus internis umbonalibus fortibus: tergorum[Pg 103]
acumine basali truncato, margini occludenti pæne
parallelo.

Valves 5; carina with a truncated and crested base;
scuta with strong internal umbonal teeth; terga with
the basal point truncated, almost parallel to the occludent
margin.

Maxillæ with short thick spines in the notch under
the two upper great spines; caudal appendages with
scattered bristles on their summits, and along their whole
outer margins.

General Appearance.—Capitulum rather compressed,
narrow, and produced. Valves white, tinged with orange,
smooth, moderately thin, occasionally with faint traces
of striæ radiating from the umbones. Scuta, apex pointed,
with a very slight ridge running to the umbo; basal
margin equalling two thirds of the length of the terga,
with an internal basal rim; on the under side of each
valve, beneath the umbo, there is a strong tooth. Out
of the numerous specimens, all excepting one had their
scuta unequally convex, with their occludent margins
unequally curved, that of the more convex valve at
the umbo, curling beyond the medial line. The basal
end of the carina is, likewise, slightly curved laterally,
and always turns towards the more convex valve. This
inequality, as Mr. Gray pointed out to me, depends on
the position of the specimens; the flatter side lying close
to the carapace of the crab. Terga, flat, oblong, nearly
rectangular; occludent margin straight; basal angle,
truncated, almost parallel to the occludent margin; in
width, three or four times as wide as the carina. Carina,
(fig. 1, a) short, narrow, slightly curved, upper part
broadest, with the apex rounded, only just passing up
between the basal broad ends of the terga; externally
carinated, internally very slightly concave; basal end[Pg 104]
abruptly truncated, crested, not deeply imbedded in the
membrane of the peduncle.

Peduncle, barely as long as the capitulum, apparently
(for specimens dry and much shrunk) narrow, surrounded
by rings or folds of thicker yellowish membrane, of which
the upper ones retain moderately long spines; low down
these rings become confluent; whole surface finely dotted,
dots largest on the rings.

Mouth.—Labrum highly bullate in the upper part, with
a row of teeth on the crest; mandibles with four teeth,
the fourth close to the inferior apex, which is very little
developed, sometimes making the fourth tooth appear
simply bifid. Maxillæ with two large spines on the
upper angle, beneath which there is a large depression,
bearing one rather long and thick, and four short and
thick, spines; inferior upraised part with a double row of
longer and thinner spines.

Cirri.—Posterior cirri with segments bearing five pairs
of spines, of which the lowest pair is very minute; intermediate
spines minute; spines of the dorsal tuft thin,
of nearly equal size; segments not at all protuberant,
elongated. First cirrus, standing far separated from the
second (as in Scalpellum), with its nearly equal rami
rather above half as long as those of the second cirrus.
Second cirrus with anterior ramus not thicker, and
scarcely more thickly clothed with spines, than the posterior
ramus, but shorter than it by three or four segments;
the spines not forming a very thick brush on the
anterior ramus. Both rami of third cirrus with a longitudinal
row of minute spines, parallel to the main pairs.
Between the bases of the pedicels of the first pair of cirri,
there are two closely approximate, conical flattened protuberances,
like the single one to be described in Ibla.

Caudal Appendages, about one third of the length of
the pedicel of the sixth cirrus, with some moderately long
and strong spines at the end, and down the whole outer
sides.

Ova, much pointed. Penis, hairy.[Pg 105]

Size.—Capitulum in largest specimens half an inch
long.

2. Pæcilasma aurantia. Pl. II, Fig. 2.

P. valvis 5; carinæ basi truncatâ: scutis ovatis,
margine basali perbrevi, dentibus parvis, internis, umbonalibus
instructo: tergorum acumine basali perobliquè
truncato.

Valves 5; carina with a truncated base; scuta oval,
with the basal margin very short, furnished with small
internal umbonal teeth; terga, with the basal point very
obliquely truncated.

Maxillæ with fine spines in the notch under the three
great upper spines; caudal appendages with scattered
bristles on their summits, and along only the upper part
of their outer margins.

General Appearance.—This species so closely resembles
P. Kæmpferi, that it is superfluous to describe it in
detail; and I will indicate only the points of difference.
When the valves have been well preserved, they are of
fine pale orange colour, and hence the name above given,
which was proposed by the Rev. R. T. Lowe.

Scuta, with the internal umbonal teeth small; basal
internal marginal rim very prominent, furrowed within;
basal margin short, (only equalling half the length of
terga), owing to the great curvature of the lower part of
the carino-tergal margin; hence, the outline of the scuta
is almost pointed oval. I saw no appearance of inequality
in the two sides.

Terga, rather smaller in proportion to the scuta, than in
P. Kæmpferi, with the basal end very obliquely truncated,
so as to appear at first simply pointed, not parallel to the
occludent margin; apex considerably more pointed and
produced than in the foregoing species.[Pg 106]

Carina, almost of equal narrowness throughout, barely
concave within; lower end triangular, abruptly truncated,
and not crested.

Primordial valves very plain, with the usual hexagonal
structure: those of the terga, rounded at both ends, instead
of being square, as in the mature calcified valves.

Peduncle short, narrow, not half as long as the capitulum;
paved with minute equal beads, as in the genus
Dichelaspis.

Mouth.—Mandibles with the fourth tooth very small;
inferior angle rudimentary. Maxillæ, with three great
upper spines, beneath which there is a deep notch bearing
some delicate spines; inferior upraised part, as in
P. Kæmpferi.

Cirri.—Rami of first cirrus hardly more than one
third as long as the rami of the second cirrus, which
latter rami are unequal in length by only two segments;
the posterior ramus being the longer one.

Caudal Appendages, with only two or three lateral
bristles, besides those on the summit.

Size.—Capitulum, three to four tenths of an inch long.

General Remarks.—This species has the closest general
resemblance to P. Kæmpferi, and is evidently a representative
of it. On close examination, however, almost
every part differs slightly; the chief points being the
narrowness of the basal margin of the scuta; the obliqueness
of the truncated basal end of the terga and the
sharpness of the upper end; the rudimentary state of
the inferior angle of the mandibles; the character of
the spines on the maxillæ; the proportional lengths of
the cirri, and the fewness of the spines on the outer
sides of the caudal appendages. The fact of Madeira
having this Pæcilasma, a representative both in structure
and habits of a Japan species, is interesting, inasmuch,
as I am informed by Mr. Lowe, that some of the Madeira
fishes are analogues of those of Japan.[Pg 107]

3. Pæcilasma crassa. Pl. II, Fig. 3.

P. valvis 5; carinæ termino basali in discum parvum
infossum producto: scutis convexis, dentibus internis
umbonalibus nullis: tergis pæne rudimentalibus, vix carinâ
latioribus.

Valves 5; carina with the basal end produced into a
small imbedded disc; scuta convex, without internal
umbonal teeth; terga almost rudimentary, scarcely broader
than the carina.

Spines on the segments of the posterior cirri arranged
in single transverse rows.

General Appearance.—Capitulum highly bullate, or
thick. Valves rather thick, opaque, either pale or dark
flesh-red, smooth, yet rather plainly striated from the
umbones. There are a few very minute spines on the
membranous borders of the valves.

Scuta highly convex, broadly oval, apex broad rounded;
basal margin narrow, much curved; no internal, umbonal
teeth; basal internal rim strong, running up part
of the occludent margin. A slightly prominent ridge,
either rounded or angular, but in one specimen a
narrow depressed fissure-like line, runs parallel to the
occludent margin and ends near the apex in a slight
notch; this fact is of interest in relation to the structure
of the scuta in P. eburnea and P. fissa. The scuta are
either equally or very unequally convex; in the latter case,
the occludent margin of one valve is curled, so that its
umbo is not quite medial.

Terga, minute, almost rudimentary, scarcely broader
than the carina, and half as long as the chord of its arc;
carinal margin slightly curved; scutal margin straight,
with a slight prominence fitting into a notch in the scuta;
basal end bluntly pointed.

Carina, (fig. 3, a) rather shorter than the scuta,
extending up only to the basal ends of the terga;
moderately curved; apex moderately sharp; middle part
broadest, externally carinated; internally not concave,
with the inner lamina of shell, at the basal end, produced
into a very small oblong disc or tooth, which is
only as wide as the narrowest upper part of the valve.
The exterior keel does not extend on to this disc, which
is slightly constricted at its origin.

Peduncle very short, narrow, ringed, and apparently
without spines.

Size.—Capitulum four tenths of an inch long.

The following parts of the animal are described from
some small and not well preserved specimens from
Madeira, which I owe to the kindness of Mr. Lowe.

Mouth.—Labrum highly bullate in the upper part,
with large, inwardly pointed, unequal teeth. Mandibles,
with four large, pointed, equal-sized teeth, with the inferior
angle very narrow, acuminated like a single spine.
Maxillæ, with three (?) large upper spines, of which the
middle one is extremely strong and long, beneath which,
there is a deep notch with a single strong spine, and
with the whole inferior part square and much upraised,
so as to stand on a level almost with the tips of the great
upper spines.

Cirri in a miserable state of preservation; first cirrus
short, second cirrus with rami unequal, and I suspect the
anterior one the longest; some of the other cirri also
have unequal rami. The segments of the posterior
cirri are not protuberant, they have on their anterior
faces a single transverse row of bristles: in the upper
segments, some of the spines in each dorsal tuft (which
is much spread out), are much thicker, though rather[Pg 109]
shorter than those on the anterior face. This peculiar
structure is common to all five posterior cirri.

Caudal Appendages.—I can only say that they are
spinose on their summits.

Affinities.—This species is allied to P. eburnea in the
rudimentary condition of its terga; in the disc-shaped
basal end of its carina; and in the presence in some
specimens, of a fissure-like line on the scuta parallel to
their occludent margins. Its affinity, however, is closer
to P. fissa, as is more especially shown by the remarkable
arrangement of the spines on the five posterior cirri.

4. Pæcilasma fissa. Pl. II, Fig. 4.

P. valvis 7; scuto utroque è duobus juxtapositis segmentis
formato; segmento altero intus dentato: tergis brevibus,
ter aut quater carinâ latioribus: carinæ termino basali in
discum parvum angustum infossum producto.

Valves 7; each scutum being formed of two closely
approximate segments; of which one is internally toothed:
terga short, three or four times as wide as the carina:
carina with the basal end produced into a small, narrow,
imbedded disc.

Spines on the segments of the posterior cirri arranged
in single transverse rows.

General Appearance.—Capitulum gibbous, broadly
oval, nearly a quarter of an inch long. Valves white,
smooth, moderately thick, marked by the lines of growth.
The occludent segments of the scuta, and nearly the
whole of the terga, and the whole of the carina, enveloped
in lemon-yellow membrane, tinged with orange, but the
specimen had long been kept dry.

Scuta formed of two, apparently always separate,
segments, closely united, so that externally their separation[Pg 110]
is hardly visible, and does not allow of movement;
the fissure thus formed runs almost in the line connecting
the umbo and apex, (where in most species a ridge
extends,) but a little on the carinal side of it. The
occludent segment is narrowly bow-shaped, pointed at
both ends, with the upper end projecting slightly beyond
the apex of the lateral segment, and with the occludent
margin regularly curved from end to end. The lateral
segment is large, of an oval shape, with a narrow strip
cut off on one side. Primordial valves very plain at the
umbones of the lateral segments, but none are visible on
the occludent segments; and this makes me believe that
these two pieces are normally parts of a single valve;
having only one specimen of P. fissa, I was not able to
make out quite certainly whether the two segments are
continuously united at their umbones by a non-calcified
portion of valve, as is certainly the case with Dichelaspis.
The basal margin of the lateral segment is narrow,
inflected, and blends with the carino-tergal margin; it
has an internal, prominent, basal rim, and towards the
occludent margin a large, prominent, internal tooth. This
internal basal rim is not parallel to the outer basal
margin, but rises to a point a little way up the occludent
margin, in the same manner as in P. eburnea, but in
a lesser degree; in this latter species the peduncle is
internally almost cut off by the large disc of its carina;
here, on the other hand, it is internally almost cut off by
these rims and the two large teeth of the lateral segments
of the scuta.

Terga sub-triangular, short, nearly half as broad as
long; three or four times as wide as the carina, and rather
wider than the occludent segment of the scuta; occludent
margin single, arched; carinal margin slightly arched;
basal angle bluntly pointed.

Carina very narrow, much arched, running up just
between the basal ends of the terga; exterior ridge enveloped
in membrane; heel blunt, prominent; internally,
not concave, even slightly convex, produced at the lower[Pg 111]
end into a very narrow, short, imbedded disc, (or rather
tooth,) which is itself a little curved downwards and
blunt at the end.

Peduncle very narrow, about half as long as the
capitulum; yellow, finely beaded, plainly ringed, without
spines.

Mouth.—Labrum, with a row of minute teeth; palpi
narrow. Mandibles with all the lower part narrow; of
the four teeth, the second and third are narrow, the
fourth is pectinated and placed very close to the inferior
angle, which is produced into a long thin tooth. Maxillæ
unknown.

Cirri.—First pair lost. The arrangement of the spines
on all is most abnormal, Pl. X, fig. 29: dorsal tuft long,
arranged in a transverse line and seated in a deep notch;
in the sixth cirrus, the spines on the lower segments are
fine, those on the upper segments are thick and claw-like,
mingled with some fine spines; in the four anterior
cirri the spines of the dorsal tufts are even thicker
and more claw-like. On the anterior faces, also, of all
the segments the spines form a single row; they are
shorter than those composing the dorsal tuft; hence the
spines on each segment are arranged in a circle, interrupted
widely on the two sides: this arrangement is
common to all five posterior cirri. Second cirrus, with
the anterior ramus one third longer and thinner than
the posterior ramus (this is the reverse of the usual
arrangement); this longer ramus equals in length the
sixth cirrus. Third cirrus, with the anterior ramus considerably
longer than the posterior ramus; in the three
posterior pair of cirri, also, the anterior rami are a little
longer than the posterior: except in length, there is
little difference of any kind between the five posterior
pair of cirri. Pedicels of the cirri long; rami rather
short; segments elongated, not protuberant.

Caudal Appendages nearly as long as the pedicels of the
sixth cirrus, thickly clothed with very fine bristles, like a
camel’s-hair pencil brush.[Pg 112]

Affinities.—In the structure of the carina, and more
especially of the scuta, there is a strong affinity between
the present and following species; for we shall immediately
see that in P. eburnea there is evidence of the
scuta being composed of two segments fused together;
and the larger segment is furnished with an internal
oblique, strong, basal rim. To this same species there is
an evident affinity in the form of the mandibles and of the
caudal appendages, and in the anterior rami of the cirri
being longer than the posterior rami. Notwithstanding
these points of affinity, I consider that P. fissa is more
closely related in its whole organisation, as more particularly
shown in the arrangement of the spines on the
cirri and in the presence of terga, to P. crassa than to
P. eburnea. Although in Dichelaspis, the scuta are
invariably composed of two almost separate segments,
yet P. fissa shows no special affinity to this genus.

5. Pæcilasma eburnea. Pl. II, Fig. 5.

P. valvis 3; scutis acuminatis, ovatis; ad pedunculum
pæne transversè spectantibus; dentibus internis umbonalibus
fortibus: tergis nullis: carinæ termino basali in
discum amplum oblongum infossum producto.

Valves 3; scuta pointed, oval, placed almost transversely
to the peduncle; internal umbonal teeth strong:
terga absent: carina with the basal end produced into a
large, oblong, imbedded disc.

Spines on the upper segments of the posterior cirri,
arranged in three or four approximate longitudinal rows,
making small brushes.

General Appearance.—Capitulum flat, pear-shaped,[Pg 113]
placed almost transversely to the peduncle. Valves
white, smooth, moderately thick.

Scuta: the basal margin, as seen externally, is narrow,
and can hardly be separated from the carinal margin;
but an internal basal rim, (fig. 5, b) (along which the
imbedded disc of the carina runs,) shows where, in
the other species, the basal and carinal margins are
separated. This basal internal rim is not parallel to the
external basal margin, but runs upwards to the occludent
margin, leaving beneath it a large triangular space, to
which the membrane of the peduncle is attached; and
this makes it appear as if the rostral umbones of these
valves had grown downwards; but, judging from the
allied species, P. fissa, I have no doubt that the primordial
valves really lie on the umbones, and that the
growth has been in the usual direction, that is, exclusively
upwards. The occludent margin is curved, and
blends by a regular sweep into the carinal margin, so
that there is no acute upper angle. A distinct line can
be seen, as if two calcareous valves had been united,
running from the umbo to the upper end of the valve,
thus in appearance separating a slip of the occludent
margin; internally this appearance is more conspicuous;
this structure is important in relation to that of P. fissa.
The pointed umbones are divergent, and internally under
each, there is a large tooth. The two valves are equally
convex.

Terga, entirely absent.

The Carina (Tab. II, fig. 5, a, c), including the disc,
is three fourths as long as the scuta; it is placed almost
transversely to the longitudinal axis of the peduncle; it is
narrow and internally convex; the imbedded disc is very
large, forming a continuous curve with the upper part of
the carina; this disc runs along the internal basal rim of
the scuta, and hence almost separates, internally, the
peduncle from the capitulum; it equals one fourth of the
total length of the valve, and is thrice as wide as the
upper part; it is oval, externally marked by a central[Pg 114]
line, and with a slight notch at the end, giving a divided
appearance to the whole, and indicating how easily a fork
might be formed from it. The carina is thick, measured
from the inner convex to the exterior surface, which is
carinated; heel prominent.

Peduncle, narrow, very short, not nearly so long as the
capitulum.

Mouth.—Labrum considerably bullate, with the lower
part much produced towards the adductor muscle; crest
with small bead-like teeth; palpi small, pointed; mandibles,
with the first tooth standing rather distant from
the second; inferior angle spine-like and bifid; maxillæ
(Pl. X, fig. 15), with two considerable spines (only one is
shown in the Plate) beneath the upper large pair; the
inferior upraised part bears seven or eight pair of spines,
and its edge is not quite straight; close to the main
notch, lying under the four upper spines, there are two
minute notches, with the interspace bearing a tuft of fine
spines and a pair of larger ones.

Cirri.—The rami in all are rather unequal in length,
the anterior rami being rather the longest; the anterior
rami of the second and third cirri are not thicker than
the posterior rami. The segments in the three posterior
cirri are not protuberant; the upper segments bear three
or four pair of spines, with some minute intermediate
ones, and with the lateral marginal spines unusually large
and long, so as to form, with the ordinary pairs, a third
or fourth longitudinal row; hence a small brush is formed
on each segment. The dorsal tuft is large and wide, so as
to contain even fourteen spines, of which some are as long
as those in front. In the lower segments of these same
posterior cirri, the lateral marginal spines are not so much
developed (nor is the dorsal tuft), and hence the segments
can hardly be said to be brush-like. The first cirrus is
placed rather distant from the second pair. The second
and third cirri differ from the three posterior pair, only
in the bristles being slightly more numerous, and in the
dorsal tufts being more spread out.[Pg 115]

Caudal Appendages about half the length of the lower
segments of the pedicels of the sixth cirrus; truncated and
rounded at their ends; thickly clothed with long excessively
fine bristles, so as to resemble camel-hair pencils.

The Stomach, I believe, is destitute of cæca; in it was
a small crustacean.

General Remarks.—I was at first unwilling to sacrifice
Mr. Hind’s genus, Trilasmis, which is so neatly characterised
by its three valves; moreover, the present
species does differ, in some slight respects, from the
other species of Pæcilasma; but under the head of
P. fissa I have shown how that species, P. crassa and
P. eburnea are tied together. The absence of terga,
which are rudimentary in P. crassa, (and we shall hereafter
see, in Conchoderma, how worthless a character their
entire absence is,) and the arrangement of the spines
in the upper segments of the posterior cirri, are the only
characters which could be used for a generic separation.

Genus—Dichelaspis. Plate II.

Valvæ 5, quæ ferè pro septem haberi possent, scuto in
segmenta planè duo, ad angulum autem rostralem conjuncta,
diviso: carina plerumque sursum inter terga extensa,
deorsum aut disco infosso aut furcâ aut calyce terminata.

Valves 5, generally appearing like 7, from each scutum
being divided into two distinct segments, united at the
rostral angle; carina generally extending up between the
terga terminating downwards in an imbedded disc, or
fork, or cup.

Mandibles, with three or four teeth; maxillæ notched,
with the lower part of edge generally not prominent;
anterior ramus of the second cirrus not thicker than the
posterior ramus, not very thickly clothed with spines;
caudal appendages uniarticulate, spinose.

Description.—The capitulum appears to contain seven
valves; but, on examination, it is found that two of the
valves on each side, are merely segments of the scutum;
these are united at the umbo, in three of the species, by a
narrow, non-calcified portion of valve, where the primordial
valve is situated; in D. orthogonia, however, the junction
of the two segments is perfectly calcified, and of the
same width as the whole of the basal segment. The
capitulum is much compressed, broad at the base, and
extends a little beneath the basal segments of the scuta.
The valves are very thin, often imperfectly calcified, and
generally covered with membrane. They are not placed
very close together, and in all the species a considerable
interspace is left between the carina and the two other
valves: in the D. Grayii the valves are so narrow that
they form merely a calcified border round the capitulum.
The membrane between the valves and over them, is
very thin, and is thickly studded, in some of the species,
with minute blunt conical points, apparently representing
spines. The valves in the same species present considerable
variations in shape; in their manner or direction of growth,
and in the position of their primordial valves, they agree
with Lepas and Pæcilasma.

Scuta.—In three of the species the two segments,[Pg 117]
named the occludent and basal, appear like separate
valves, but these, by dissection, can be most distinctly
seen to be united at the rostral angle. The primordial
valve, formed of the usual hexagonal tissue, is elliptic,
elongated, and placed in the direction of the occludent
segment; calcification commences at its upper point, so
as to form the occludent segment, and afterwards at its
lower point, but rectangularly outwards, to form the basal
segment; in the minute space between these two points
of the primordial valve, there is, in four of the species,
no calcification; so that the two segments are united by
what may be called a flexible hinge; in D. orthogonia the
two calcareous segments are absolutely continuous. The
occludent segment is longer than the basal segment; it
either runs close along the orifice, or in the upper part
bends inwards; both segments are narrow, except in
D. Warwickii, in which the basal segment is moderately
broad; the two segments are placed at an angle, varying
from 45° to 90°, to each other. The capitulum generally
extends for a little space beneath the basal segments of
the scuta, where it contracts to form the peduncle.

The Terga present singular differences in shape, and
are described under the head of each species; scarcely
any point can be predicated of them in common, except
that they are flat and thin.

The Carina is much bowed, narrow, and internally
either slightly concave or convex and solid; the upper
end extends far up between the terga; the lower end is
formed by a rectangularly inflected, imbedded, triangular
or oblong disc, deeply notched at the end, or as in
H. Lowei, of a fork, the base, however, of which is wider
than the rest of the carina, so as to present some traces of
the disc-like structure of the other two species; or lastly,
as in D. orthogonia, it terminates in a crescent-formed
cup.

Peduncle.—This is narrow, compressed, and about as
long, or twice as long, as the capitulum; in D. Warwickii
it is studded with minute beads of yellowish chitine.[Pg 118]

Size.—Small, with a capitulum scarcely exceeding a
quarter of a inch in length.

Filamentary Appendages.—None. There are two small
ovigerous fræna, which, in D. Warwickii, had the glands
collected in seven or eight little groups on their margins.

Mouth.—Labrum highly bullate, with small teeth on
the crest; palpi small, not thickly covered with spines.
Mandibles narrow, with three or four teeth. Maxillæ
small, with a notch beneath the two or three great upper
spines; lower part bearing only a few pair of spines,
generally not projecting, but in D. orthogonia largely
projecting. Outer maxillæ, with their inner edges continuously
covered with bristles.

Cirri.—First pair short, situated rather far from the
second pair; second pair with the anterior ramus not
thicker than the posterior ramus, and hardly more thickly
clothed with spines than it, excepting sometimes the few
basal segments. All the five posterior pair of cirri resemble
each other more closely than is usual. In
D. Lowei, the segments of the posterior cirri bear the
unusual number of eight pair of main spines.

Caudal Appendages.—Uni-articulate, spinose; in D.
pellucida they are twice as long as the pedicels of the
sixth cirrus, but I could not perceive in them any distinct
articulations.

General Remarks.—Four of the five species, forming
this genus, though certainly distinct, are closely allied. I
have already shown, that although the characters separating
Lepas, Pæcilasma, and Dichelaspis are not very important,
yet if they be neglected these three natural little
groups must be confounded together. Dichelaspis is
much more closely united to Pæcilasma than to Lepas,
and, as far as the more important characters of the
animal’s body are concerned, there is no important difference[Pg 119]
between them. Consequently, I at first united
Pæcilasma and Dichelaspis, but the latter forms so natural
a genus, and is so easily distinguished externally, that I
have thought it a pity to sacrifice it. The carina, (which
seems to afford better characters than the other valves in
Dichelaspis,) from generally running up between the terga
and in ending downwards, in three of the species, in a
deeply notched disc or fork, more resembles that in
Lepas than in Pæcilasma; in the manner, however, in
which the imbedded disc, in D. Warwickii and D. Grayii,
nearly cuts off the inside of the capitulum from the
peduncle, there is a resemblance to Pæcilasma eburnea.
In the extent to which the valves are separated from
each other, in the bilobed form of the scuta, (the two
segments in Dichelaspis, perhaps, answering to the upper
and lateral projections in the scuta of Conchoderma virgata,)
and in the basal half of the scuta not descending
to the base of the capitulum, there is a considerable resemblance
to Conchoderma; in both genera the adductor
muscle is attached under the umbones of the scuta; but
the structure of the mouth and cirri and caudal appendages
shows that the affinity is not stronger to Conchoderma than
to Lepas. It appears at first probable, that Dichelaspis
would present a much closer affinity to Pæcilasma fissa, in
which, owing to the scuta being formed of two segments,
there are seven valves, than to any other species of
that genus; but in P. fissa the primordial valve is triangular
and is situated on the basal segment, whereas, in
Dichelaspis, it is elliptic and is seated between the two
segments, and is more in connection with the occludent
than with the basal segment; and this I cannot but think
is an important difference: in other respects, P. fissa
shows no more affinity to Dichelaspis than do the other
species of the genus. Finally, I may add that Dichelaspis
bears nearly the same relation to Pæcilasma, as Conchoderma
does to Lepas.[Pg 120]

1. Dichelaspis Warwickii. Pl. II, figs. 6, 6 a, b.

D. scutorum segmento basali duplo latiore quam segmentum
occludens: tergorum parte inferiore paulò latiore
quam occludens scutorum segmentum.

Scuta, with the basal segment twice as wide as the
occludent segment; terga, with the lower part slightly
wider than the occludent segment of the scuta.

Mandibles, generally with four teeth.

General Appearance.—Capitulum much compressed,
elongated, with the valves not very close together, the
carina being separated by a rather wide space from the
scuta and terga. Valves variable in shape, very thin and
translucent, covered by thin membrane, which, over the
whole capitulum, is studded with minute blunt points.

Scuta.—Segments without internal teeth or an internal
basal rim; the occludent segment long, narrow, pointed,
not quite flat, sometimes slightly wider in the upper
part; about one third of its own length longer than
the basal segment; occludent margin slightly arched;
basal segment about twice as wide as the occludent segment,
triangular, slightly convex; in young specimens
(Pl. II, fig. 6 b), the carinal margin of the basal segment
is protuberant, and the occludent margin hollowed out; in
old specimens the occludent margin of the basal segment
is straight, and the carinal margin much hollowed out.
In very young specimens the basal segment is very small
compared to the occludent.

Terga, variable in shape; flat, lower part wider than
the occludent segment of the scuta; occludent margin[Pg 121]
double, forming a considerable rectangular projection,
as in the terga of Lepas; scutal margin deeply excised at
a point corresponding with the apex of the scuta, a flat
tooth or projection being thus formed; there is sometimes
a second tooth (fig. 6 b) a little above the basal
point. The terga, in the first variety, somewhat resemble
in shape the scuta of Conchoderma aurita.

Carina, much bowed, narrow, slightly concave within,
(in the Borneo specimen, rather wider and more concave,)
extending up between the terga for half their
length, terminating downwards in a rectangularly inflected,
deeply imbedded, oblong, rather wide, flat disc,
at its extremity more or less deeply notched. This disc
is externally smooth; internally it sometimes has two
divergent ridges on it; it extends across about two-thirds
of the base of the capitulum (fig. 6 a, as seen
from beneath, when the peduncle is cut off), to under
the middle of the basal segments of the scuta.

Peduncle, narrow, flattened; united to the capitulum
some little way below the scuta; about as long as the
capitulum; the membrane of which it is composed is
thin, externally studded with bluntly conical beads of
yellowish chitine, of which the largest were 1/2000 of an
inch in diameter; on their internal surfaces these are
furnished with a small central, circular depression, apparently
for a tubulus; the arrangement of the beads varied
in concentric zones. Similar conical points on the capitulum
have an internal concave surface about 1/3000 in
diameter, with a central circle 1/12000 in diameter, for the
insertion, as I believe, of a tubulus.

Size.—The largest specimen had a capitulum a quarter
of an inch long.

Mouth.—Labrum highly bullate; crest with not very
minute, blunt teeth, which towards the middle lie closer
and closer to each other, so as to touch. Palpi rather
small, with a few very long bristles at the apex.

Mandibles, narrow, produced, with four teeth, and the
inferior angle tooth-like and acuminated; in one specimen,[Pg 122]
on one side of the mouth, the mandible had only
three teeth.

Maxillæ, small; at the upper angle there are two large
spines and a single small one, beneath which there is a
deep notch, and beneath this a straight but projecting
edge, bearing a few moderately large and some smaller
spines. Outer maxillæ sparingly covered with bristles
along the inner margin.

Cirri.—First pair far removed from the second pair,
and not above half their length; segments rather broad,
with transverse rows of bristles not very thickly crowded
together; terminal segments very obtuse, and furnished
with thick spines. The segments of the three posterior
pair have each three or four pair of spines, with a few
minute spines scattered in an exterior, parallel, longitudinal
row; dorsal tufts, with four or five long spines.
The second cirrus has its anterior ramus not thicker,
but rather shorter than the posterior ramus; the former
is only a little more thickly clothed with spines, owing
to those in the longitudinal lateral row being longer and
more numerous, than is the sixth pair of cirri. Bristles
not serrated.

Caudal Appendages, narrow, thin, slightly curved, about
half as long as the pedicels of the sixth cirrus; in young
specimens, the appendage bore seven or eight pair of long
bristles rectangularly projecting; in some older specimens,
there was a tuft of bristles on the summit, and two
other tufts on the sides.

I at first thought that the Borneo specimen was a
distinct species, but after careful comparison of the external
and internal parts, the only difference which I can
detect is, that the terga are slightly larger, and that the
carina, to a more evident degree, is wider, more especially
in the middle and lower portions.[Pg 123]

2. Dichelaspis Grayii. Pl. II, fig. 9.

D. scutorum segmento basali angustiore quam segmentum
occludens; longitudine pæne dimidiâ: tergis bipenniformibus,
margine crenato, spinâ posticâ, manubrio
angustiore quam occludens scutorum segmentum.

Scuta, with the basal segment narrower than the occludent
segment, and about half as long as it. Terga like
a battle-axe, with the edge crenated and a spike behind;
the handle narrower than the occludent segment of the
scuta.

Mandibles with three teeth; cirri unknown.

General Appearance.—Capitulum much compressed,
elongated, formed of very thin membrane, with the valves
forming round it a mere border. Valves thin, imperfectly
calcified, covered with membrane.

Scuta formed of two narrow plates at very nearly
right-angles to each other, one extending along the
occludent, and the other along the basal margin; both
become very narrow at the point of junction, and are
there not calcified, but are evidently continuous and form
part of the same valve; the basal segment is about half
as long and narrower than the occludent segment, flat
and bluntly pointed at the end; occludent segment
slightly curled, and therefore the whole does not lie
quite in the same plane; narrow close to the umbo,
with a very minute tooth on the under side; apex
rounded. In the upper part, the occludent segments
leave the membranous margin of the orifice, and run in
near to the terga, bending towards them at an angle of
45° with their lower part. I was unable to distinguish
the primordial valves.[Pg 124]

Terga.—These valves are of the most singular shape,
resembling a battle-axe, with a flat and rather broad
handle; the upper part consists of an axe, with a broad
cutting crenated edge, behind which is a short blunt
spike. The spike and cutting edge together answer to
the double occludent margin of the tergum in Lepas.
The whole valve is flat, thin, and lies in the same plane;
the carinal margin is nearly straight; the scutal margin
bulges out a little, and at a short distance above the blunt
basal point is suddenly narrowed in, making the lowermost
portion very narrow; the widest part of the handle
of the battle-axe, is narrower than the occludent segment
of the scuta. The two spikes behind the cutting and
crenated edges of the two terga, are blunt and almost
touch each other; above their point of juncture, the membrane
of the orifice forms a slight central protuberance.

Carina, very narrow throughout, concave within, much
bowed; upper point broken and lost, but it must have
run up between the terga for more than half their
length; basal portion inflected at nearly right angles,
and running in between, and close below, the linear
basal segments of the scuta, so as almost entirely to
cut off internally the peduncle and capitulum. This
lower inflected and imbedded portion, or disc, gradually
widens towards its further end, which is, at least, four times
as wide as the upper part of the carina, and is deeply
excised, but to what exact extent I cannot state, as the specimen
was much broken. On each side of this elongated
triangular disc, there is a slight shoulder corresponding
to the ends of the basal segments of the scuta; and on
the upper surface of each shoulder, there is a small tooth
or projection. The middle part of the disc is barely
calcified, and is transparent.

Peduncle, rather longer than, and not above half as
wide as, the capitulum; the latter being nearly 2/10ths
of an inch in length: the membrane of the peduncle is
thin, naked and structureless.

Mouth.—Labrum highly protuberant in the upper part,[Pg 125]
with a row of beads on the crest. Palpi small, with few
bristles. Mandibles, with the whole inferior part, very
narrow; three teeth very sharp, with a slight projection,
perhaps, marking the place of a fourth tooth; inferior
angle ending in the minutest point; first tooth as far
from the second, as the latter from the inferior angle.
Maxillæ with a broad shallow notch; inferior angle much
rounded, bearing only four or five pair of spines.

Cirri.—First pair apparently remote from the second
pair; all five posterior pair lost; first pair short, with
the rami unequal by about two segments; segments
clothed with several transverse rows of bristles; terminal
segments blunt.

3. Dichelaspis pellucida. Pl. II, fig. 7.

D. valvarum singularum acuminibus superioribus et
inferioribus vix intersecantibus: scutorum segmento basali
multo angustiore quam segmentum occludens; longitudine
ferè dimidiâ: tergis bipenniformibus, margine integro,
manubrii acumine ad carinam flexo.

Valves with the upper and lower points of the several
valves only just crossing each other. Scuta with the basal
segment much narrower than the occludent segment, and
about half as long as it. Terga like a battle-axe, with
the edge smooth, and the point of the handle bent towards
the carina.

Mandibles with four teeth; caudal appendages twice
as long as the pedicels of the sixth cirrus.

This species comes very close to the D. Grayii, which
likewise was attached to a snake; but I cannot persuade
myself, without seeing a graduated series, that the differences
immediately to be pointed out can be due to
ordinary variation. I am much indebted for specimens
to the kindness of Mr. Busk.[Pg 126]

General Appearance.—The membrane of the capitulum
and peduncle is surprisingly thin and pellucid, so that
the ovarian tubes within the peduncle can be traced with
the greatest ease. The valves are small, the apices only
just crossing each other, and are composed of yellow
chitine, with mere traces of calcification. The capitulum
is pointed, oval, .15 of an inch long; the peduncle is
narrow, and fully twice as long as the capitulum.

Scuta.—The two segments stand at right-angles to
each other; the basal segment is linear and pointed,
fully half as long, but only one third as wide, as the
occludent segment. The point of junction of the two
segments is wider than the rest of the basal segment.
This latter segment lies some little way above the top of
the peduncle. The occludent segment is bluntly pointed;
it is directed a little inwards from the edge of the orifice
towards the terga; the apex reaches up just above the
slightly reflexed lower point of the terga. The adductor
muscle is fixed under the point of junction of the two
segments.

The Terga are battle axe-shaped, with the blade part
very prominent, smooth-edged; behind the blade there is
a short upwardly-turned prominence. The lower point
of the handle of the axe, is bent towards the carina. The
tergum, measured in a straight line, equals in length
two thirds of the occludent segment of the scutum, the
handle being rather narrower than this same segment.

The Carina is extremely narrow and much bowed; the
apex reaches up only to just above the lower bent points
of the terga. The basal end is rectangularly inflected, and
stretches internally nearly across the peduncle; it consists
(fig. 7 a) of a triangular disc of yellow thin membrane,
four or five times as wide as the upper part of the valve;
the end of this disc is hollowed out; its edges are thickened
and calcified, and hence, at first, instead of a disc,
this lower part of the carina appears like a wide fork;
the tips of the prongs stretch just under the tips of the
basal segments of the scuta.[Pg 127]

Peduncle.—Its narrowness and transparency are its
only two remarkable characters.

Mouth.—All the parts closely resemble those of
D. Grayii, but being in a better state of preservation I
will describe them. The labrum is highly bullate, with
a row of minute teeth on the crest, placed very close
together in the middle. Palpi small, thinly clothed with
spines; mandibles extremely narrow, hairy, with four
teeth, but the lower tooth is so close to the inferior
angle, as only to make the latter look double. Maxillæ,
with a very deep broad notch, dividing the whole into
two almost equal halves; in the upper part there are
three main spines.

Cirri.—The first pair are placed at a considerable distance
from the second pair; they are short with equal
rami, and rather broad segments furnished with a few
transverse rows of bristles. The five posterior cirri have
singularly few, but much elongated segments, bearing
four pair of spines: the two rami of the second pair are
alike, and differ only from the posterior cirri in a few
of the basal segments having a few more spines.

The Caudal Appendages are twice as long as the pedicels,
and nearly half as long as the whole of the sixth
cirrus; they have a small tuft of long thin spines at their
ends, and a few in pairs, or single, along their whole
length; at first I thought that they were multi-articulate,
but after careful examination I can perceive no distinct
articulations; I have seen no other instance of so long
an appendage without articulations.

Diagnosis.—This species differs from D. Grayii in all
the valves being shorter, so that their points only just
cross each other; but this, I conceive, is an unimportant
character. In the scuta, the basal segment is here narrower,
but the point of junction of the two segments
wider than in that species; in the terga, the edge of the
axe is smooth instead of being crenated, and the handle
and the point behind are of a rather different shape; in
the carina the imbedded basal disc has not shoulders and[Pg 128]
small teeth, as in D. Grayii. Notwithstanding these
differences, I should not be much surprised if the present
form were to turn out to be a mere variety.

4. Dichelaspis Lowei. Pl. II, fig. 8.

D. scutorum segmento basali angustiore quam occludens
segmentum, longitudine ferè 4/5: tergorum parte inferiori
duplo latiore quam occludens scutorum segmentum.

Scuta with the basal segment narrower than the occludent
segment, and about four-fifths as long as it. Terga
with the lower part twice as wide as the occludent segment
of the scuta.

Mandibles with four teeth; segments of the three posterior
cirri with eight pair of main spines.

General Appearance.—Capitulum much compressed,
sub-triangular, formed of very thin membrane; valves imperfectly
calcified, and thin.

Scuta formed of two narrow plates placed at about an
angle of 50° to each other, and united at the umbo by a
non-calcified flexible portion. The primordial valve is
situated at this point, but chiefly on the occludent segment.
The occludent segment is about twice as wide
and about one fifth longer than the basal segment, which
latter is rather sharply pointed at its end. The occludent
segment is slightly arched, a little narrowed in on the
occludent margin close to the umbo; its upper end is
broad and blunt; it runs throughout close to the edge of
the orifice of the sack, and its longer axis is in the same
line with that of the terga. Close to the umbones, on
the under side of the basal segment, there is, on each
valve, a longitudinal calcified fold, serving as a tooth.[Pg 129]

Terga broad, with a deep notch corresponding to the
apex of the occludent segment of the scuta; the part
beneath the notch is of nearly the same width throughout,
and is twice as broad as the occludent segment of the
scuta; it has its basal angle very broad and blunt. The
entire length of the terga equals two thirds of that of the
occludent segment of the scuta; occludent margin simply
and slightly curved.

The Carina is of nearly the same width throughout,
with the upper part rather the widest, and the apex
blunt; within convex; it extends up between three fourths
of the length of the terga, terminating downwards in a
fork with very sharp prongs, standing at right-angles to
each other (fig. 8 a.) The fork, measured from point to
point, is thrice as wide as, and measured across at the
bottom of the prongs it is wider than, the widest upper
part of the valve,—a resemblance being thus shown with
the triangular notched disc in D. Grayii. The points
of the prong extend under about one fourth of the length
of the basal segments of the scuta.

Peduncle rather longer than the capitulum, which, in
the largest specimen, was 2/10ths of an inch in length;
peduncle narrow, close under the capitulum; membrane
thin and structureless. The larger specimen had almost
mature ova in the lamellæ.

Mouth.—Labrum with a few bead-like teeth on the
crest, distant from each other even in the central part;
palpi rather small, moderately clothed with bristles.

Mandibles, with four teeth; the inferior angle blunt
and broad, showing, apparently, a rudiment of a fifth
tooth; the first tooth is as far from the second, as is this
from the inferior angle; second, third, and fourth teeth
very blunt, whole inferior part of mandible not much narrowed.
Maxillæ small, with a small notch under the
three upper spines, which are followed by five or six pair,
nearly as large as the upper spines.

Cirri.—First pair remote from the second; their rami
nearly equal, and about one third of the length of the[Pg 130]
rami of the second cirrus; thickly clothed with bristles:
rami of the second cirrus of equal thickness, but little
shorter than those of the sixth cirrus; the three or four
basal segments of the anterior ramus are thickly clothed
with spines; the other segments, and all the segments
on the third pair, resemble the segments of the three
posterior pair. These latter are elongated, not protuberant,
and support eight pairs of spines with very
minute intermediate spines; those in the dorsal tufts are
numerous and long.

Caudal Appendages nearly as long as the pedicels of the
sixth cirrus; oval, moderately pointed, with their sides,
for one fourth of their length, thickly clothed with long
very thin spines.

Affinities.—In the form of the scuta and of the carina
this species is most nearly allied to D. Grayii or D. pellucida,
in the form of the terga to D. Warwickii.

5. Dichelaspis orthogonia. Pl. II, fig. 10.

D. scutorum basali segmento angustiore quam occludens
segmentum; longitudine ferè dimidiâ; duorum segmentorum
junctione calcareâ: tergorum prominentiis marginalibus
inæqualibus quinque: carinâ deorsum in parvo calyce
lunato terminatâ.

Scuta with the basal segment narrower than the
occludent segment, and about half as long as it; junction
of the two segments calcified. Terga with five unequal
marginal projections. Carina terminating downwards in
a small crescent-formed cup.

Maxillæ with the inferior part of edge much upraised.

The specimens are in a bad condition, not one with
all the valves in their proper positions, and most of them
broken; animal’s body much decayed and fragile.[Pg 131]

General Appearance.—Capitulum apparently much
flattened; valves naked, coloured reddish, separated from
each other by thin structureless membrane.

The Scuta consist of two bars placed at right-angles to
each other, with the point of junction fully as wide as
any part of the basal segment, and perfectly calcified;
the primordial valve lies at the bottom of the occludent
segment. The basal segment is equally narrow throughout,
and very slightly concave within; the occludent
segment widens a little above the junction or umbo, and
then keeps of the same width to the apex, which is
obliquely truncated; internally this segment is concave;
externally it has a central ridge running along it; the
occludent segment is twice as long and twice as broad as
the basal segment. Both segments are a little bowed
from their junction to their apices.

Terga.—These are of a singular shape; they are about
three-fourths as long as the occludent segment of the
scuta, and in their widest part, of greater width than it.
They consist of four prominent ridges proceeding from
the umbo, and united together for part only of their
length, and, therefore, ending in four prominences; one
of these, the longest, has the same width throughout,
and forms the basal point; a second, very small one, is
seated high up on the carinal margin just above the apex
of the carina; the third and fourth, are nearly equal in
length, and project one above the other on the scutal
margin. There are two occludent margins, meeting each
other at right angles, and forming a prominence, as in
Lepas; and this gives to the margin of the valve the five
prominences. The whole valve internally is flat; externally,
it is ridged as described.

Carina (fig. 10, a, b), much bowed, narrow, long;
externally, the central ridge is quite flattened; internally,
slightly concave, but scarcely so towards the lower part,
which is narrow; the upper part widens gradually, and the
apex is rounded. The basal embedded portion is as
wide as the uppermost part, and forms a cup, unlike anything[Pg 132]
else known: the outline of this cup is semi-oval and
crescent-formed; it is moderately deep; it is formed by
the external lamina of the carina bending rectangularly
downwards and a little outwards, whereas the inner
lamina of the lower part (which is slightly concave), is
continued with the same curve as just above, and forms
the concave chord to the semi-oval rim of the cup. This
cup, I believe, lies under the points of the basal segments
of the scuta.

Peduncle unknown, probably short.

Length of capitulum, above 2/10ths of an inch.

Mouth.—Labrum with the upper part highly bullate,
and produced into a large overhanging projection; crest
with a row of rather large bead-like teeth; palpi small,
their two sides parallel, very sparingly covered with long
bristles.

Mandibles, narrow, produced, with four teeth, and
the inferior angle produced into a single strong spine:
the distance between the tips of the first and second teeth
almost equals that between the tip of the second tooth
and of the inferior angle.

Maxillæ with three large upper unequal spines, beneath
which, there is a deep and wide notch (bearing one spine),
and the inferior part projects highly, bearing three or
four pairs of spines, and is, itself, obscurely divided into
two steps.

Outer Maxillæ, very sparingly covered with bristles;
outline, hemispherical.

Cirri.—The rami of the five posterior pair are extremely
long, as are the pedicels; the segments are much elongated,
with their anterior faces not at all protuberant;
each bears five pair of very long and thin spines, with an
excessively minute one between each pair; the dorsal tuft
consists of very fine and thin spines. The second cirrus
has its anterior ramus not at all thicker than the posterior
ramus; but has an exterior third longitudinal row of
small bristles. First cirrus, separated by a wide interval
from the second pair; very short with the two rami[Pg 133]
slightly unequal in length; the segments are broad, and
are paved moderately thickly with spines; the terminal
spines not particularly thick.

Caudal Appendages consist of very small and narrow
plates, about half the length of the pedicels of the sixth
cirrus, with a few long spines at their ends.

This well-marked species, I think, has not more affinity
to one than to another of the previous species: it differs
from all, in the junction between the two segments of the
scuta being perfectly calcified; in the peculiar cup, forming
the base of the carina; and lastly, in the inferior part of
the maxillæ projecting.

Oxynaspis.[33] Gen. Nov. Pl. III.

Valvæ 5, approximatæ: scutorum umbones in medio
marginis occludentis positi: carina rectangulè flexa, sursùm
inter terga extensa, termino basali simpliciter concavo.

Valves 5, approximate; scuta with their umbones in
the middle of the occludent margin; carina rectangularly
bent, extending up between the terga, with the basal end
simply concave.

Mandibles with four teeth; maxillæ notched, with the
lower part of edge nearly straight, prominent; anterior
ramus of the second cirrus thicker than the posterior
ramus; caudal appendages, uniarticulate, spinose.

I have most unwillingly instituted this genus; but it
will be seen by the following description, that the one
known species could not have been introduced into Lepas
or Pæcilasma, without destroying these genera, although
it has a close general resemblance with both. As far as the
valves are concerned, it is more nearly related to Lepas
than to Pæcilasma; but taking the entire animal, its[Pg 134]
relation is much closer to the latter genus than to Lepas:
it differs from both these genera in the manner of growth
of the scuta, which is both upwards and downwards, the
primordial valve being situated in nearly the middle of
the occludent margin. In this respect, and in the shape
of the carina and terga, there is an almost absolute identity
with Scalpellum; I may, however, remark that in Scalpellum,
the scuta first grow downwards, and afterwards
in most of the species upwards, whereas here from the
beginning, the growth is both upwards and downwards.
In the mouth and cirri, there is rather more resemblance
to Scalpellum than to Pæcilasma and Lepas: in habits,
also, this genus agrees with Scalpellum, and if it had
possessed a lower whorl of valves, it would have quite
naturally entered that genus. It is unfortunate, that so
insignificant and poorly characterised a form should require
a generic appellation. In natural position, it appears to
lead from Scalpellum through Pæcilasma to Lepas.

1. Oxynaspis celata. Pl. III, fig. 1.

General Appearance.—The capitulum is rather thin,
and broad in proportion to its length; it seems always
entirely covered by the horny muricated bark of the
Antipathes, and hence externally is coloured rich brown
and covered with little horny spines. The membrane
over the valves is very thin, and is with difficulty separated
from the Antipathes; it has, I believe, no spines of
its own. The corium lining the peduncle is a fine
purple. All the individuals are attached to the coralline,
with their capitulums upwards in the direction of the
branches, and in this respect fig. 1. is erroneous.

The valves, when cleared of the bark, are white, or are
strongly tinged with pinkish-orange. The upper parts
of the scuta and terga are plainly furrowed in lines[Pg 135]
radiating from their umbones; hence their margins are
serrated with blunt teeth; their surfaces, moreover, are
sparingly studded with small calcareous points.

Scuta (fig. 1, a), sub-triangular, with the lower part
rounded and protuberant, the upper produced and pointed.
The umbo is situated in the middle of the occludent
margin, instead of at the rostral angle, as in the foregoing
genera. The occludent margin is straight, and is bordered
by a narrow step or ledge, formed of transverse growth-ridges,
and therefore has its edge serrated: the rostral
angle is often slightly produced into a small projection.
The basal margin is short, and forms an angle above a
rectangle with the occludent margin: the tergal margin
is straight; the carinal margin is rounded, protuberant,
and of unusual length compared to the basal margin. The
surface of the valve is convex near the umbo; and beneath
there is a large deep hollow for the adductor muscle.

Terga (fig. 1, b) large, flat, triangular, as long as the
scuta or the carina, all three valves being nearly equal in
length; occludent margin straight, or slightly arched,
basal angle broad, not very sharp.

Carina short (fig. 1, c, drawn rather too long), deeply
concave, rectangularly bent, with the lower part not quite
as long as the upper, and a little wider: the basal margin
is truncated, rounded, and slightly sinuous. The umbo
is situated at the angle, and therefore nearly central.
The umbo of the terga, I may add, is in the same place,
as in Lepas.

The peduncle is very short and narrow, and is, I believe,
without spines; it is enveloped by the bark of the Antipathes.
The capitulum in the largest specimens was
.2 of an inch in length.

Filamentary Appendages, apparently none.

Mouth, with the orifice rather inclined abdominally.

Labrum, with the upper part extremely protuberant,
forming a projecting horn; no teeth on the crest. Palpi
rather small, with only a few bristles at the end.

Mandibles, with four teeth and the inferior angle[Pg 136]
pointed: first tooth as far from the second, as is the latter
from the inferior angle; in one specimen, on one side,
there were five teeth.

Maxillæ with three great spines at the upper angle,
beneath which a deep notch, and with the inferior part
much upraised; this lower part rather rounded at both
corners, with the upper spines longer than the lower.

Outer Maxillæ, with the bristles continuous in front;
externally, slightly protuberant, with a tuft of bristles
longer than those on the front side. Olfactory orifices
apparently not protuberant; but all the specimens were
in a bad state.

Cirri.—Prosoma very little developed. First cirrus
very far removed from the second. The three posterior
cirri are straight and long; the segments are elongated
and bear four or five pairs of very long spines, with a
single minute intermediate spine between each pair;
dorsal tufts, with long spines. First cirrus, rami unequal
by two or three segments, and thickly covered with spines;
the first cirrus is short compared to the second, owing to
the length of the pedicel of the latter, though the longer
ramus of the first, nearly equals the shorter ramus of the
second pair. Second cirrus, with its anterior ramus
shorter by two or three segments than the posterior
ramus, and thicker than it, with the segments covered like
brushes with bristles; posterior ramus, and both rami of
the third cirrus, a little more thickly clothed with bristles
than are the three posterior cirri.

Caudal Appendages, minute, broadly oval, with six or
seven long bristles on their summits.

Genus—Conchoderma. Plate III.

Valvæ 2 ad 5, minutæ, inter se remotæ: scuta bi-aut
tri-lobata, umbonibus in medio marginis occludentis
positis: carina arcuata, terminis utrinque pæne similibus.

Valves 2 to 5, minute, remote from each other: scuta
with two or three lobes, with their umbones in the
middle of the occludent margin: carina arched, upper
and lower ends nearly alike.

Filaments seated beneath the basal articulations of the
first pair of cirri, and on the pedicels of four or five anterior
pairs; mandibles, with five teeth, finely pectinated;
maxillæ step-formed; caudal appendages, none.

The Capitulum is formed of smooth membrane, including
five small valves, of which the terga and carina
are often quite rudimentary or absent. Valves minute,
thin, generally more or less linear, placed far distant from
each other; sometimes imperfectly calcified and covered
by chitine membrane, or imbedded in it. The umbones[Pg 138]
of the valves (together with the primordial valves) are nearly
central, so that they are added to at their upper and lower
ends; hence their manner of growth is considerably different
from that of the valves in Lepas. The adductor
muscle is attached to a slight concavity on the under side
of each scutum, at the point whence the lobes diverge.

The Terga are placed almost transversely to the scuta;
at their lower ends, there is either a very slight prominence
in the capitulum, or there is a large tubular, folded appendage,
opening into the sack, and apparently serving
for respiratory purposes.

Peduncle, smooth, moderately long; attachment effected
by the cement-stuff being poured out exclusively, as it
appears, from the larval antennæ. These antennæ in
C. aurita and C. virgata, resemble, in the form of the
disc and in the long feathered spines on the ultimate segment,
those in Lepas.

The Filamentary Appendages are highly developed;
there are six or seven on each side; two are attached
beneath the basal articulation of the first cirrus (as is usual
in Lepas), and near them there are one or two small
pap-formed projections of apparently similar nature; the
rest of the filaments are attached to the posterior edges
low down, on the lower segments of the pedicels of the
cirri. I believe, in all cases, these appendages are occupied
by testes.

Prosoma, moderately developed.

Mouth, situated not far from the adductor muscle;
labrum considerably bullate, with the crest hairy and
pectinated with inwardly pointing, approximate, flattened
teeth: inner fold of the supra-œsophageal cavity slightly
thickened and yellowish, villose on the sides.

Palpi of the usual shape, not meeting, moderately
broad.

Mandibles, with five teeth, graduated in size, nearly
equidistant, finely pectinated either on one or both sides
towards their bases; inferior angle narrow, either produced
into a fine tooth, or almost rudimentary.[Pg 139]

Maxillæ, about 3/4ths of the size of the mandibles, step-formed,
with five steps generally distinct; at the upper
angle there are two large unequal spines, of which the
lower one is the largest, with a third long thin one on
the first step; lower spines doubly serrated. Apodeme
directed inwards and backwards.

Outer Maxillæ (Pl. X, fig. 16) simply arched; the
membrane of the supra-œsophageal cavity under these
maxillæ is highly bullate and villose. Olfactory orifices
not prominent.

Cirri.—First pair not seated far distant from the
second pair. The three posterior pair have the anterior
faces of their segments considerably protuberant, supporting
four or five pairs of long bristles; between which,
there is a row of minute, fine, upwardly pointing bristles:
on the lateral upper margins of each segment, there are
a few very minute spines; dorsal tuft short, with thick
and thin spines intermingled. In the first cirrus (of
which the rami are nearly equal in length), and in the
anterior ramus of the second cirrus, the faces of the segments
are highly protuberant, and clothed with thick
transverse rows of finely and doubly serrated spines: the
anterior ramus of the second cirrus is considerably thicker
than the posterior ramus, which latter, together with
both rami of the third cirrus, differ from the three posterior
cirri only in the intermediate and in the lateral
marginal spines being slightly more developed.

Caudal Appendages, absent.

Alimentary Canal.—The upper part of the stomach has
four large cæca, of which the posterior one is the largest;
the whole surface, also, is covered with minute pits,
arranged in transverse rows.

Generative System, developed to an extraordinary degree.
The testes run into all the filamentary appendages,
as well as more or less, into the pedicels of the
cirri: the two vesiculæ seminales unite within the penis,
either just beyond its basal constriction, or up one third
of its length. Penis short, hairy. The ovarian tubes not[Pg 140]
only fill the peduncle, but extend in a thin sheet between
the two folds of corium all round the sack, close up to
the terga. The two ovigerous fræna are present in the
usual position; the ovigerous lamellæ either form several
layers, in pairs, one under the other, or are united in a
single large cup-formed sheet enclosing the whole animal.

Colours.—The prevailing tint is a dark purplish-brown,
which forms, or tends to form, broad longitudinal
bands on the peduncle and capitulum.

General Remarks.—This genus is intimately related,
as has been remarked by Professor Macgillivray,[36] to
Lepas: if we look to the body of the animal, which from
being less exposed to external influences must, in the
Cirripedia, offer the most trustworthy characters, we find
that in Conchoderma there are additional filamentary appendages
attached to the cirri, that there are no caudal
appendages, that the teeth of the mandibles are finely
pectinated, and that the ovarian tubes run higher up round
the sack; in every other respect, there is the closest similarity,
even to the arrangement of the bristles on the
cirri. In the capitulum, the difference consists chiefly,
though not exclusively, in the less development of the
valves, and their consequent wide separation: the scuta,
however, in Conchoderma, are added to beneath their
umbones, or original centres of growth, which is never the
case, or only to a very slight degree, in Lepas. Conchoderma
has no very close affinity to any other genus. As the
majority of authors have ranked the two common species
under two distinct genera (Otion and Cineras), I may
observe, that there is no good ground for this separation;
in the above few specified points in which Conchoderma
differs from the genus most closely allied to it, the two
species essentially agree together. If we take the nearest
varieties of C. virgata and C. aurita, there is but a very
slight difference even in the form of their valves, and
these hold the same relative positions to each other; the[Pg 141]
carina, however, is always less developed in C. aurita;
even the colouring in both tends to follow the same
arrangement. The only obvious distinction between the
two species, are the ear-like appendages of C. aurita,
which, however, are not developed in its early age, are
subject to considerable variation, are of no high functional
signification, and are indicated in C. virgata by two
prominences on the same exact spots. On these grounds
I conclude, that the generic separation of the two species
is quite inadmissible.

1. Conchoderma aurita. Pl. III, fig. 4.

C. capitulo duobus tubularibus quasi-auribus instructo,
pone terga rudimentalia (sæpe nulla) positis: scutis bilobatis:
carinâ nullâ, aut omnino rudimentali: pedunculo
longo, a capitulo distincte separato.

Capitulum with two tubular ear-like appendages, seated
behind the rudimentary and often absent terga; scuta
bilobed; carina absent, or quite rudimentary; peduncle
long, distinctly separated from the capitulum.

Filaments attached to the pedicels of the second cirrus;
two upper spines of the maxillæ pectinated.

General Appearance.—The capitulum (seen from above
in Pl. III, fig. 4 a) is slightly compressed, almost globular,
composed of thick membrane, with two large, ear-like,
flexible, tubular, folded appendages, at the upper end,
opening into the sack. These appendages are seated
behind the rudimentary terga when such are present, or
behind the spots which they would have held if not
aborted. In a young condition they are tubular, but not
folded; and often, according to Prof. Macgillivray, either
one or both are at first imperforate. They are formed externally
of the outer membrane of the capitulum (rendered
thin where folded), and internally of a prolongation of
the inner tunic of the sack; between the two, there is,
as around the whole sack, a double layer of corium. A
section across both appendages, near their bases, is given
in Pl. III, fig. 4 b, showing how they are folded,—the
chief fold being directed from below upwards, with a
smaller fold, not always present, from between the two,
outwards. The folds sometimes do not exactly correspond
on opposite sides of the same individual; they are
almost confined to the lower part, the orifice itself being
often simply tubular. These appendages are sometimes
very nearly as long as the whole capitulum: a section[Pg 143]
near their bases is sub-triangular. I shall presently make
some remarks on their functions and manner of formation.

The Scuta, as well as the other valves, are imperfectly
calcified: shape, variable. They usually consist of two
lobes or plates, placed at above a right angle to each
other, and rarely (fig. 4 c) almost in a straight line; the
lower lobe is more pointed and narrower than the upper;
the two correspond to the lower and middle lobes in the
scuta of C. virgata, the upper one being here absent.

The Terga are developed in an extremely variable
degree; they are often entirely cast off and absent. In
very young specimens, they are of the same length with
the carina, but after the carina has ceased to grow, the
terga always increase a little, and sometimes to such a
degree as to be even thirty or forty times as long as
carina. When most developed (fig. 4 a) they are not
above one third as long as the scuta, to which they lie
at nearly right angles; they consist of imperfectly calcified
plates, square at both ends, slightly broader and thinner
at the end towards the carina, where they are a little
curled inwards, than at the opposite end; they are not
quite flat in any one plane; internally they are slightly
concave; finally, I may add, they nearly resemble in
miniature the terga of C. virgata. In full grown specimens,
the terga almost invariably drop out and are lost; but
even in this case, a long brownish cleft in the membrane
of the capitulum, marks their former position. The
orifice of the capitulum is usually notched between the
terga, or between the clefts left by them; on each side
of the notch there is a slight prominence. In some few
cases, however, there is no trace of this notch. Behind
the terga or the clefts, the great ear-like appendages, as
we have seen, are situated.

Carina, rudimentary (fig. 4.) and often absent; it is
pointed-elliptical, and is rarely above the 1/40th of an inch
long. After arriving at this full size, calcareous matter
is added to the under surface over a less and less area, so
that it becomes internally pointed, and finally, in place of[Pg 144]
calcareous matter, continuous sheets of chitine are spread
out beneath it; hence, during the disintegration of the
outer surface, the carina comes to project more and more,
and at last drops out; subsequently, even the little hole
in which it was imbedded, disintegrates and disappears.

Peduncle, cylindrical, distinctly separated from the
capitulum, and generally twice or thrice as long as it:
the thickness of the outer membrane generally great, but
variable: surface of attachment variable, either pointed,
or widely expanded, or formed into divergent projections.

Filamentary Appendages, seven on each side, highly
developed, long and tapering; there are two beneath the
basal articulation of the first cirrus, and one on the posterior
margin of the pedicel of each cirrus, excepting the
sixth pair; the filaments on the pedicels are nearly twice
as long as the cirri themselves.

Mouth,—mandibles, with the five teeth nearly equidistant,
and towards their bases finely pectinated on both
sides; inferior angle rudimentary, often represented by a
single minute spine: in one specimen, there were only
four teeth on one side. Maxillæ, with five steps, not very
distinct from each other, with the first step much curved.
The larger of the two upper great unequal spines is
pectinated, like the teeth of the mandibles; there is a
third long finer spine beneath the upper large pair.

Cirri rather short, broad, with the anterior faces of
the segments protuberant, especially those of the first
cirrus and of the anterior ramus of the second pair: spines
on the anterior cirri doubly serrated. Posterior cirri, with
the intermediate spines between the pairs, long; dorsal
tufts, minute. On the lower segment of the pedicels of the
four posterior cirri, there are two separate tufts of bristles.

Colours extremely variable; sometimes five longitudinal
bands of dark purple can be distinctly seen (as in C. virgata)
on the peduncle, these bands becoming more or less
confluent on the capitulum; at other times, the capitulum
is more or less spotted, or often nearly uniformly purple:
the sack, cirri and trophi are, also, purple.[Pg 145]

Size.—The largest specimen which I have seen was,
including the peduncle and ears, five inches in length,
the capitulum itself being rather above one inch in length,
and 7/10ths of an inch in breadth.

General Remarks.—I have come to the same conclusion
with Prof. Macgillivray, concerning the variability of this
form, and I believe there is only one true species. With
respect to Dr. Coates’s species, viz., Otion depressa and
O. saccutifera, though I have not seen specimens, I can
hardly doubt, from the insufficient characters given, that
they are mere varieties.

With respect to the ear-like appendages, we shall presently
see in C. virgata, that at corresponding points on
the capitulum (Tab. III, fig. 2 b), there are two slight,
closed prominences. According to Professor Macgillivray,
in C. aurita, every gradation can be followed by which
the appendages, at first closed, become tubular and open.
The opening would ensue, if the corium became absorbed
at the bottom of the appendages whilst still imperforate,
for then the inner tunic would be cast off at the next
moult and would not be re-formed, whilst the outer
membrane would gradually disintegrate together with the
other external parts of the capitulum, and not being
re-formed at this point, an aperture would at last be left.
These appendages have no relation to the generative
system: the ovarian tubes, which surround the sack do
not extend into them; nor do the ovigerous lamellæ. I
believe, that their function is respiratory: the corium
lining them is traversed by river-like circulatory channels,
and their much-folded, tubular and open structure must
freely expose a large surface to the circumambient water.
Why this species should require larger respiratory organs
than any other, I know not. In this species, moreover,
the filamentary appendages are developed to a greater
extent than in any other cirripede; in most genera, the
surface of the body and of the sack suffices for respiration.[Pg 146]

2. Conchoderma virgata. Pl. III, fig. 2. Pl. IX, fig. 4.

C. Scutis trilobatis: tergis intùs concavis, apicibus introrsùm
leviter curvatis: carinâ modicâ, leviter curvatâ:
pedunculo in capitulum coalescente.

Scuta three-lobed: terga concave internally, with their
apices slightly curved inwards: carina moderately developed,
slightly curved: peduncle blending into the
capitulum.

No filament attached to the pedicel of the second cirrus.

Var. chelonophilus (Pl. III, fig. 2 c). Terga, minute,
nearly straight, solid, acuminated at both ends, placed
far distant from the other valves: carina, either minute[Pg 147]
and acuminated at both ends, or moderately developed
and slightly arched and blunt at both ends: lateral lobes
of the scuta broad: valves imperfectly calcified.

General Appearance. Capitulum, flattened, gradually
blending into the peduncle; summit square, rarely obtusely
pointed. Membrane, thin. Valves, thin, small,
sometimes imperfectly calcified, very variable in shape and
in proportional length, and therefore, situated at variable
distances from each other, but always remote and imbedded
in membrane.

Scuta, trilobed, consisting of an upper and lower lobe
(the latter generally the broadest), united into a straight
flat disc, with a third lobe standing out from the middle
of the exterior margin, generally at an angle of from
50° to 70° (rarely at right angles) to the upper part, and
generally (but not always) bending a little inwards. The
shape of the lateral lobe varies from rounded oblong to an
equilateral triangle; as it approaches this latter form, it
becomes much wider than the upper or lower lobes. In
one specimen, and only on one side, the scutum (fig. 2 d)
presented five points or projections. In some specimens,
the scuta are very imperfectly calcified, and consist of
several quite separate beads of calcareous matter of irregular
shape, held together by tough brown membrane.

Terga, extremely variable in shape, placed at nearly
right angles to the scuta: beyond their carinal ends
(fig. 2 b), the capitulum presents two small prominences,
which are important as indicating the position of the
homologous, ear-like appendages in C. aurita.[39] The
upper ends of the terga are imbedded in membrane, and
project freely like little horns for about one third of their
length: this free portion exactly answers to the projecting[Pg 148]
portion, bounded by the two occludent margins,
in the terga of Lepas. The freely projecting portion is
generally curled inwards, and the carinal portion more
or less outwards,—the form of the letter S being thus approached;
but the curvatures are not exactly in the same
plane. The whole valve is generally of nearly equal width
throughout, the carinal part being a very little (but in some
specimens considerably) wider; internally, it is deeply
concave; both points generally are blunt and rounded. In
some rare varieties (Cineras chelonophilus of Leach, fig. 2 c),
the terga are much smaller and flat, with both points sharp,
the whole upper portion being much and abruptly attenuated,
and internally, without a trace of a concavity.
Generally, the terga are about two thirds of the length
of the scuta, rarely only half their length; generally,
they are separated from the apices of the scuta by about
their own length, rarely by twice their own length.
Generally, the terga are shorter than the carina, but
sometimes a very little longer than it: generally they are
distant by one third or one fourth of their own length
from the apex of the carina, rarely by their entire length.