Conchoderma have received thirty-three different specific
denominations, caused partly by changes of nomenclature, and
partly from varieties having ranked as species.
_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.
_Distribution._--Mundane, throughout the equatorial, temperate,
and cold seas; attached to floating objects, living or
inorganic.
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 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-oesophageal 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.
_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-oesophageal 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 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 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.
[36] Remarks on the Cirripedia, &c.; ‘Edin. New Phil. Journal,’
vol. xxxix, p. 171.
1. CONCHODERMA AURITA. Pl. III, fig. 4.
LEPAS AURITA. _Linn._[37] Systema Naturæ, 1767.
OTION CUVIERANUS (!) BLAINVILLIANUS (!) BELLIANUS (!)
DUMERILLIANUS (!) RISSOANUS. _Leach._ Encyclop. Brit., vol.
iii, Supp., 1824, and Zoological Journal, vol. ii, p. 208,
July 1825.
OTION DEPRESSA et SACCUTIFERA. _Coates._ Journal Acad. Nat. Sci.
of Philadelphia, vol. vi, p. 132, 1829.
OTION AURITUS. _Macgillivray._ Edinburgh New Phil. Journal, vol.
xxxviii, 1845.
LEPAS LEPORINA. _Poli._ Test. utriusq. Sicil., pl. vi, fig. 21,
1795.
LEPAS CORNUTA. _Montagu._ Linn. Trans., vol. xi, p. 179, 1815.
CONCHODERMA AURITUM et LEPORINUM. _Olfers._ Magaz. der Gesell.
Freunde zu Berlin, 3d Quartel., p. 177, 1814.
BRANTA AURITA. _Oken._ Lehrbuch der Naturgesch., Th. 11, p. 362,
1815.
MALACOTTA BIVALVIS. _Schumacher._ Essai d’un Nouveau Syst., &c.,
1817.
GYMNOLEPAS CUVIERII. _De Blainville._ Dict. des Sc. Nat., Art.
Mollusc., Plate, fig. 1, 1824.
[37] Many authors (Poli, Montagu, &c.,) have doubted from the
strangely mistaken description, viz., “ore octovalvi dentato,”
whether this species could be the _Lepas aurita_ of Linnæus. But
in the Linnean Society, there is a proof plate from Ellis’s
“Account of several rare Species of Barnacles,” in ‘Phil.
Trans.,’ 1758, with an excellent figure of the _C. aurita_, and
on the margin in Linnæus’s handwriting is the name _Lepas
aurita_.
_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.
_Hab._--Mundane; extremely common. On ships’ bottoms from all
parts of the world. Arctic Sea. Greenland. Pacific Ocean. Often
attached to Coronulæ on Whales. On slow-moving fish, according
to Dr. A. Gould. Often associated with _C. virgata_, and _Lepas
anatifera_, _L. Hillii_, and _L. anserifera_.
_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 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 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.
_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.
2. CONCHODERMA VIRGATA. Pl. III, fig. 2. Pl. IX, fig. 4.
LEPAS VIRGATA. _Spengler._ Skrifter Naturhist. Selbskabet., B. i,
1790, Tab. vi, fig. 9.
---- CORIACEA. _Poli._ Test. utriusque Sicil., Pl. vi, fig. 20,
1795.
---- MEMBRANACEA. _Montagu._ Test. Brit. Supp., p. 164, 1808, et
Linn. Trans., vol. xi, Tab. xii, fig. 2.
CONCHODERMA VIRGATUM. _Olfers._ Magaz. Gesells. Naturfor. Freunde,
Berlin, 1814, p. 177, (3d Quartel).[38]
BRANTA VIRGATA. _Oken._ Lehrbuch der Gesell., Th. ii, p. 362,
1815.
SENOCLITA FASCIATA. _Schumacher._ Essai d’un Nouveau Syst., 1817.
CINERAS VITTATA. _Leach._ Encyclop. Brit. Supp., Tom. iii, Plate.
1824.
---- CRANCHII (!) CHELONOPHILUS (!) OLFERSII (!). _Leach._
Tuckey’s Congo Expedition, p. 412, 1818.
---- MEGALEPIS (!) MONTAGUI (!) RISSOANUS. _Leach._ Zool. Journal,
vol. ii, p. 208, 1825.
---- MEMBRANACEA. _Macgillivray._ Edin. New Phil. Journal, vol.
xxxix, p. 171, 1845.
---- BICOLOR. _Risso._ Hist. Nat. des Productions, &c., 1826, Tom.
iv, p. 383.
---- VITTATUS. _Brown._ Illust. of Conch., 1844, Pl. li, figs.
16-18.
GYMNOLEPAS CRANCHII. _De Blainville._ Dict. des Sci. Nat. Hist.,
1824.
PAMINA TRILINEATA (!) (Var. Monstr.). _J. E. Gray._ Annals of
Phil., vol. x, 1825.
[38] See page 136 respecting this date.
_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 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.
_Hab._--Mundane: extremely common on ships’ bottoms from all
parts of the world. Falkland Islands. Galapagos Islands, Pacific
Ocean. Attached to sea-weed, turtle and other objects. Often
associated with _Conchoderma aurita_, _Lepas anatifera_, _L.
Hillii_, and _L. anserifera_.
_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 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.
[39] These have also been observed by Dr. Coates; see ‘Journal of
Acad. Nat. Sci. Philadelphia,’ vol. vi, p. 134, 1829.
_Carina_ (fig. 2 _a_), lying nearly parallel to the scuta, concave
within, very slightly bowed, of nearly the same width throughout, but
with the lower third beneath the umbo, generally a trace wider than the
upper part. Length, variable, generally rather longer (sometimes by even
one third of its own length) than the scuta, but sometimes equalling
only three fourths of the length of the scuta; generally longer than the
terga. Upper and lower points rounded; in rare varieties, both ends are
sharply acuminated. The carina and terga are generally most acuminated
where they are smallest and least perfectly calcified; and consequently,
in this same state, the valves stand furthest apart.
_Peduncle_, flattened, gradually widening as it joins the capitulum, to
which it is generally about equal in length, or a little longer.