A Monograph on the Sub-class Cirripedia Part 14

_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 h.o.m.ologous, 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 ac.u.minated. The carina and terga are generally most ac.u.minated 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.

_Filamentary Appendages._--Six on each side (Pl. IX, fig. 4), of which one (_h_) is seated on the posterior margin of a swelling, beneath the basal articulation of the first cirrus, and this is the longest; the second (_g_) is short and thick, and is seated a little lower on the side of the prosoma, (near to this, there are also two little pap-like eminences;) the third (_i_) is seated on the posterior margin of the pedicel of the first cirrus, above the basal articulation; the fourth, fifth, and sixth (_j_, _k_, _l_) in similar positions on the pedicels of the third, fourth, and fifth cirri. These three latter filaments are shorter and smaller than the first three. At the base of the second cirrus, which has no proper filament, there is a swelling as if one had been united to it.

_Mouth._--_Mandibles_, with the basal edges of the five teeth pectinated by minute, short, strong spines on one side; inferior angle extremely short. In one specimen, there was a minute pectinated tooth between the first and second; in another, the second tooth was bifid on its summit; in another, the fourth was rudimentary.

_Maxillae_, with five steps: sometimes each step commences with a spine rather larger than the others; at the upper angle, there are two large unequal spines (neither pectinated,) with a third longer and thinner, seated a little below. _Outer maxillae_ (Pl. X, fig. 16), simple.

_Cirri_, with twice as many segments in the sixth cirrus as in first; spines on the first and second cirri doubly serrated.

_Colours_ (when alive).--Capitulum and peduncle grey, with a tinge of blue, with six black bands, tinged with purplish brown. The two bands near the carina become confluent on the peduncle, and sometimes disappear; the carina is edged, and the inters.p.a.ce between the two scuta, coloured with the same dark tint. The whole body and the pedicels of the cirri are dark lead-colour, with the segments of the cirri almost black: in some specimens, the colour seems laterally abraded from the cirri. Ova white, becoming in spirits pinkish, and then yellow. The dark bands on the capitulum and peduncle become in spirits purple; but are sometimes discharged; the general grey tint disappears. Professor Macgillivray states that many individuals are light-brown or yellowish-grey, with irregular brown streaks, or crowded dots: he states that in very young specimens the colours are paler, and the valves spicular.

_Size._--The largest specimen which I have seen, had a capitulum rather above one inch long and three fourths of an inch wide: growth very rapid.

_Monstrous Variety._--In the British Museum, there is a dried and somewhat injured specimen of a monstrous variety, the _Pamina trilineata_ of J. E. Gray: it differs from the common form only in having a tubular projection, just behind the notch separating the upper points of the terga; this tube springs from over the terga, and is, therefore, in a different position from the ear-like appendages in _Conchoderma aurita_. It does not open into the sack: the membrane composing it appears to have been double in the upper part, and to have been lined with corium: in short, this tube seems to have been an excrescence or tumour, of a cup or tubular form.

_General Remarks._--It will have been seen how much subject to variation the valves of this species are. When I first examined the _Cineras chelonophilus_ of Leach, from 36 N. lat., Atlantic Ocean, and found in many specimens, both old and young, that the terga were very small, flat, ac.u.minated at both ends, with a projecting shoulder on the carinal margin, and situated at about their own length from the apex of the carina, and at twice their own length from the scuta; and when I found the carina ac.u.minated at both ends, and the scuta very imperfectly calcified, with the lateral lobe broad, flat, and standing out at right angles; and lastly, when I found the whole capitulum bluntly pointed, instead of being square on the summit, I had not the least doubt, that it was a quite distinct species. Afterwards, I found in the _Cineras Olfersii_ of Leach, from the South Atlantic, the same form of terga; but within slightly more concave or furrowed, and not nearly so small, and therefore not placed at above half so great a distance from the other valves; and here, the carina had its usual outline, as had nearly the scutum on one side, whereas, on the other side, it presented a new and peculiar form, having five ridges or points, and was imperfectly calcified; seeing this, it was impossible to place much weight in the precise form or size (and therefore, relative separation,) of the calcified valves; and on close examination, I found every part of the mouth and cirri identical in Leach's _Cineras chelonophilus_ and _C.

Olfersii_, and in the common form. Therefore, I conclude, that _C.

chelonophilus_, and still more _C. Olfersii_, are only varieties; the terga presenting the greatest, yet variable, amount of difference, namely, in their ac.u.mination and flatness. We know, also, that in the species of the closely allied genus of Lepas, the terga are very variable in shape, and this is the case, even in a still more marked degree, in _Conchoderma aurita_. Professor Macgillivray, I may add, has come to a similar conclusion regarding the extreme variability of the valves of this species.

As the varieties here mentioned are very remarkable, and may perhaps turn out to be true species, I think they are worth describing in some detail: I will only further add, that we must either make several new species, or consider, as I have done, several forms as mere varieties.

C. VIRGATA, var. CHELONOPHILUS of _Leach_. Pl. III, fig. 2 _c_.

Atlantic Ocean, 35 15' N., 16 32' W. On the Testudo caretta.

Capitulum not above half an inch long, composed of very thin membrane, with six bands (as stated by Leach) of faint colour; summit bluntly pointed; valves very small, far distant from each other; the scuta are imperfectly calcified, the central part of the umbo consisting of thick, brown chitine, with imbedded sh.e.l.ly beads; terga and carina perfectly calcified.

_Scuta_ trilobed, flat, within slightly concave, upper lobe rather more ac.u.minated than the lower; lateral lobe triangular in outline, twice as wide as either the upper or lower lobes; lying in the same plane with them and standing out at almost exactly right angle.

_Terga_, flat; placed obliquely to the scuta, and barely half as long; separated from them by nearly twice their own length; upper and lower points ac.u.minated; the umbo on the carinal margin forms a projecting shoulder; the scutal margin is straight, they are separated by nearly their own length from the apex of the carina.

_Carina_ narrow, very slightly arched, within slightly concave, both points ac.u.minated; lower third rather wider than the upper part; in length equalling three fourths of the scuta, and longer by one third than the terga; about as wide as the latter.

_Filaments, Cirri, and Mouth_ exactly as before.

In some specimens sent to me by the Rev. R. T. Lowe from off the _Testudo caretta_, taken near Madeira, the scuta have their lateral lobes broad and nearly rectangular: the carina extends nearly to between the terga: the terga are nearly straight, somewhat pointed at both ends, distant from the scuta, almost solid within, with their upper points bowed outwards: the whole capitulum is bluntly pointed, as in the _var.

chenophilus_, to which form this makes a rather near approach.

C. VIRGATA, var. OLFERSII.

CINERAS OLFERSII. _Leach._ Tuckey's Congo Expedition.

_Hab._ South Atlantic Ocean.

_Scuta_, unlike on the opposite sides of the same individual, on one side with a single lateral lobe as usual, but this very narrow, on the other (fig. 2 _d_), with five lobes or projections.

_Terga_ slightly concave within, separated by a little more than their own length from the tips of the scuta, and by one third of their own length from the tip of the carina.

_Carina_ longer than the scuta by about one fifth or one sixth of its own length, blunt at both ends, considerably bowed.

Again, I possess a group of remarkably fine specimens given me by Mr. L.

Reeve, from the southern ocean, (as I infer from a young _Lepas australis_ adhering to them,) in which all the individuals, young and old, are characterised as follows:--Scuta, with the lateral lobe generally broad, but to a very varying extent, with the upper and lower lobes extremely sharp. Terga separated from the scuta, by one and a fourth of their own length, and by their own length from the carina; somewhat ac.u.minated at both ends, nearly straight, with a very slight shoulder near the umbo. Carina equalling the terga in length, and about three fourths of the length of the scuta; neither the upper nor lower point much ac.u.minated. All the valves most imperfectly calcified: in one specimen, the scutum on one side was simply h.o.r.n.y, without a particle of calcareous matter. The summit of the capitulum nearly intermediate in outline between the common square, and bluntly-pointed form of _var.

chelonophilus_. I compared the cirri and trophi with those of a common variety, and could detect not the smallest difference. This variety differs from _var. Olfersii_, in the less development of its carina, and from _chelonophilus_, in the greater development of its carina, and especially of its terga. It would appear as if the great variability of the valves was connected with the absence of calcareous matter.

3. CONCHODERMA HUNTERI. Pl. III, fig. 3.

CINERAS HUNTERI. _R. Owen._ Cat. Mus. Coll. of Surgeons, (1830), Invert. Part I., p. 71.

_C. valvis angustis: scutis trilobatis, prominentia laterali non latiore quam inferior: tergorum parte superiore paene rectangule secundum aperturae marginem flexa: carina valde arcuata: pedunculo brevi, in capitulum coalescente._

Valves, narrow: scuta, trilobed, with the lateral lobe not wider than the lower one: terga, with the upper part bent almost rectangularly along the margin of the orifice: carina considerably arched: peduncle short, blending into the capitulum.

No filament attached to the pedicel of the second cirrus.

_Var._--Carina absent; scuta, with the upper lobe absent; terga, with the rectangular projection little developed.

Attached to the skin of a snake, probably the Hydeus or Pelamis bicolor, and therefore from the tropical Indian or Pacific Oceans. Mus. Coll. of Surgeons.[40]

[40] I owe to the kindness of Professor Owen, an examination of these specimens, and information regarding them.

_Capitulum_, with the membrane very thin; summit obtusely pointed.

Valves linear and thin.

_Scuta_, elongated, flat, with the upper projecting lobe rather more ac.u.minated than the lower, and equalling it in length; lateral lobe not wider than the lower, and about as long as it, forming an angle of about 55 with the upper one.

_Terga_, of somewhat variable length, generally about half as long as the carina, narrow, and of nearly equal width throughout; lower point sharp; externally convex; internally solid, with a trace of a central depressed line; the upper fourth part generally a little bowed out of the plane of the lower part, and abruptly bent at rather above a right angle along the occludent margin of the orifice. These valves are situated at about half their own length from the upper points of the scuta.

_Carina_ considerably arched, extending to the lower points of the terga, or running up between them for even half their length; equally narrow throughout; scarcely broader than the terga; both points rounded; internally concave; the lower point does not extend as far down as that of the lower lobe of the scuta.

_Peduncle_, narrow, shorter than the capitulum, which, in the largest specimen was 4/10ths of an inch long. Longitudinal purple bands appear to have originally existed on the peduncle.

_Filamentary Appendages, trophi and cirri_ all similar to the same parts in _C. virgata_; but perhaps the anterior faces of the segments in the posterior cirri are rather less protuberant; perhaps also the first cirrus is rather shorter in proportion to the sixth cirrus.

_Variety_ (_monstrous_).--Amongst the specimens, I found one very young one, in which the scuta had not upper lobes, so that in outline they exactly resembled the scuta in the quite distinct _C. aurita_: there was not even a rudiment of a carina: the tergum, _on one side_, was externally bordered by a projecting, semicircular, calcified disc; and the upper points of both terga showed only traces of the rectangular projection, which is the chief characteristic of _C. Hunteri_. From these traces alone, and from the specimen being mingled with the others, do I here include this variety.

_General Remarks._--I have very great doubts whether I have acted rightly in considering this as a species; but as there were many specimens, old and young, all differing remarkably from the common species, this form anyhow deserves description. The points by which it can be distinguished from _C. virgata_, are--the almost rectangular manner in which the upper portion of the tergum is bent outwards and along the orifice of the sack--the narrowness of all the valves, and especially of the lateral lobes of the scuta,--and lastly, the greater curvature of the carina, which in some specimens runs up far between the terga; had this last character been constant, it would have been an important one, but such is far from being the case. Great as are these differences in the valves, and though common to many specimens, they are not sufficient to convince me that it is a true species, and I should not be at all surprised at varieties, intermediate between it and the common form, being hereafter found;--had a name not been already attached to it, I should not have given one. In the monstrous variety described, we see to what an extent the valves may vary. The _C.

Hunteri_ approaches nearest to the var. of _C. virgata_, called by Leach _Cineras chelonophilus_, for in both, the top of the capitulum is bluntly pointed and the terga are solid within; in the _Var.

chelonophilus_, the terga and carina are minute, whereas here, though very narrow, they are much elongated. Certainly _C. chelonophilus_ has almost as strong a claim to rank as a species as _C. Hunteri_; but, in the former, by the aid of other varieties, the differences were almost reduced to the peculiarities in the terga--the valves, the most subject to variation. In _C. Hunteri_ we have other differences, and the form of the terga is even still more peculiar. I have, therefore, provisionally attached to it the specific name by which it is designated in the Museum of the College of Surgeons. From having been long kept in spirits, all aid from colour is lost.