A Monograph on the Sub-class Cirripedia Part 16

_Maxillae_, nearly two thirds of the width of the mandibles; beneath the three larger upper spines there is a considerable notch, and the whole lower part is very slightly upraised; edge irregular, with obscure traces of either two projections, or perhaps of four steps.

_Outer Maxillae_, with bristles in front continuous; exteriorly there is a slight prominence near each olfactory orifice, with a tuft of long bristles.

_Cirri_ not much elongated; first pair placed not quite close to the second; five posterior cirri nearly equal in length; pedicels long, with irregularly scattered spines,--those on the pedicel of the first cirrus beautifully and conspicuously feathered. The segments of the three posterior pair are _not_ very short or broad; very slightly protuberant, each with a long transverse, crescentic, narrow brush of bristles, which stand two or three deep in the middle, but on the sides are single: dorsal tufts long, and in the upper segments the spines are thick and claw-like. This structure is common to all the cirri. First cirrus with the rami unequal in length by two segments; from the shortness of the pedicel, this cirrus is much shorter than the second, but its rami are about two thirds of the length of those of the second cirrus. Second cirrus (and in a less degree the third cirrus), with the anterior ramus a shade broader than the posterior ramus, and rather more thickly covered with spines than are the three posterior cirri. Fifteen segments in the sixth cirrus; nine in the longer ramus of the first cirrus.

_Caudal Appendages_, rather longer than the pedicels of the sixth cirrus, composed of seven cylindrical, tapering segments, each with a circle of very fine bristles on its summit.

The acoustic (?) sacks are situated some way below the basal articulations of the first cirrus.

2. ALEPAS PARASITA.

ALEPAS PARASITA. _Sander Rang._ Man. des Mollusq., p. 364, Pl.

viii, fig. 5, 1829.[44]

ANATIFA UNIVALVIS. _Quoy_ et _Gaimard_. Annales des Sciences, Nat., tom. x, p. 234, 1827, Pl. vii, fig. 8.

---- PARASITA. _Quoy_ et _Gaimard_. Voyage de l'Astrolabe, Pl.

xciii, 1834.

TRITON (ALEPAS) FASCICULATUS. _Lesson._ Voyage de la Coquille.

Mollusc. Pl. xvi, fig. 6, tom. ii, part I, 1830, p. 442.

[44] M. Sander Rang rejects the specific name "_univalvis_," as signifying a generic character, and he has been followed in this by MM. Quoy and Gaimard themselves. This, according to the Rules of the British a.s.sociation, would hardly have been a sufficient reason, but it appears that _A. parasita_, like _A. minuta_, has a pair of h.o.r.n.y scuta or valves; and, therefore, the name _univalvis_ is too obviously false to be retained. With respect to the generic name Triton, I fully believe that it was applied by Linnaeus to the cast-off exuviae of sessile Cirripedes.

_A. apertura non prominente, capituli longitudinis 2/3 aequante: scutis corneis: longitudine tota ad 2 uncias._

Orifice not protuberant, equalling two thirds of the length of the capitulum: scuta h.o.r.n.y. Total length two inches.

Animal unknown.

Parasitic on Medusae, Mediterranean and Atlantic Oceans: south sh.o.r.e of England(?)[45]

I have not seen this species, and have drawn up the above specific character from the Plates and brief descriptions in the Voyages of the Coquille and Astrolabe. M. Lesson thinks that his species differs from that of MM. Quoy and Gaimard; but as the peculiar yellow colour of the capitulum, general shape, short cirri, habits and range, are all common to both, I believe that they are identical. There is, however, one singular difference, namely, that the cirri are coloured bright blue in the Plate in the Voyage of the Astrolabe, and yellowish in that in the Voyage of the Coquille: this possibly may have resulted from the drawing in the latter case having been made from a specimen long kept in spirits.

M. Lesson says that there are seven pair of cirri, from which I infer that this species has a pair of long, articulated, caudal appendages: he a.s.serts that each cirrus has ten segments; the cirri are short and little curled. M. Lesson remarks, that "deux languettes bifurques occupent le bas de l'ouverture ovale:" I can hardly doubt but that these are h.o.r.n.y scuta of nearly the same shape as in _A. minuta_. The whole animal seems to be extremely transparent, and of a "jaune-citron clair."

MM. Quoy and Gaimard, however, remark, that different specimens vary from white to yellow. Entire length two inches, of which the capitulum is fourteen French lines. The peduncle is narrow and short.

[45] See Foot-note, p. 159.

3. ALEPAS CORNUTA. Pl. III, fig. 6.

_A. apertura parva, leviter prominente: scutis nullis: capitulo plerumque tribus, parvis, compressis eminentiis secundum carinalem marginem instructo._

Orifice small, slightly protuberant; capitulum without h.o.r.n.y scuta; generally with three small flattened projections along the carinal margin.

Outer maxillae with the inner bristles divided into two groups; segments of the posterior cirri extremely numerous, each with one pair of main spines; inner rami of the fifth and sixth cirri rudimentary.

St. Vincent's, West Indies, attached to an Antipathes, collected by the Rev. L. Guilding.

_Capitulum_ globular, slightly flattened, smooth, translucent, entirely dest.i.tute of valves; orifice slightly projecting or tubular, parallel to the longitudinal axis of the peduncle, with the edges sinuous; it appears more tubular than it really is, from the convexity of the part of the capitulum immediately beneath the orifice. Three small, flexible, h.o.r.n.y, irregular prominences project from the carinal margin; one at the bottom of the capitulum; a second about half-way up it; and a third generally close to the orifice; but their positions vary a little, and the prominences vary still more in shape and size, being either rounded and very small, or much flattened and considerably prominent; they are imperforate; in the membrane under them a few tubuli may be seen, which are not elsewhere visible; their summits are roughened with very minute points and beads of chitine; others, still minuter, are scattered over the whole capitulum.

_Peduncle_ short, narrower than the capitulum, into which it insensibly blends; strongly wrinkled; surface of attachment wide; position with respect to the branches of the coralline, various.

_Size and Colour._--The largest specimen, including the peduncle, was half an inch in length, and 3/10ths of an inch across the capitulum; colour, after having been long in spirits, brownish-yellow.

_Filamentary Appendages_, one on each side, short, tapering and pointed; seated on the posterior margin of a slight swelling beneath the basal articulation of the first cirrus; they are about equal in length to the pedicels of this cirrus.

The _Mouth_ is directed abdominally; labrum much produced downwards, so as to be far separated from the adductor muscle; moderately bullate, forming about one third of the longitudinal axis of the entire mouth; upper part forming a slightly overhanging prominence; crest with a row of blunt, bead-like teeth, and externally to them there are numerous curved short bristles.

_Palpi_ (Pl. X, fig. 8,) unusually narrow, a little hollowed out along their inner margins; pointing towards the adductor muscle; thickly covered with doubly serrated bristles.

_Mandibles_, with either two or three teeth; inferior angle narrow and tooth-like; both sides covered with strong bristles or spines, projecting beyond the toothed edge.

_Maxillae_, with two large upper spines, and a third rather distant from them; beneath these, there is a wide notch or hollow; inferior part square, projecting, bearing six pair of moderately long spines, (of which the central one is the longest,) mingled with finer ones.

_Outer Maxillae_, with a semicircular outline; the serrated bristles in front are divided into two groups; externally there is a rounded and very considerable projection covered with long bristles. Olfactory orifices slightly prominent, approximate, seated within and just beneath the rounded projections at the base of the maxillae.

_Body._--Prosoma little developed; thorax small.

_Cirri_, extremely long, but slightly curled, capable of being protruded so as almost to touch the base of the peduncle or the surface of attachment; segments short, extraordinarily numerous. In the three posterior cirri (excepting the rudimentary rami), each segment supports two long, slightly serrated spines, with two or three minute intermediate ones, and with one or two very short, thick spines on the inner and upper lateral margins: dorsal tufts with only two or three long, fine, unequal spines. All the segments are extremely flat, broad, short, with their anterior faces not protuberant; the greater number of the segments, especially the lower ones, have very obscure articulations, to be seen only with a high power, and these can be capable of little or no movement.

_First Cirrus_ placed far from the second, with the top of its pedicel on a level with the top of the lower segment of the pedicel of the second cirrus; rami short, barely half the length of those of the second cirrus; unequal, the anterior ramus being only two thirds of the length of the posterior one; the shorter ramus contains thirteen inverted-conical segments, with one side rather protuberant; the longer ramus contains twenty-three thinner segments; the segments on both rami are clothed with bristles, arranged in two or three rows, forming narrow transverse brushes.

_Second Cirrus_, with its pedicel long, and its rami nearly equalling in length those of the sixth pair; the two rami of nearly equal length; the anterior one rather thicker than the posterior one; this posterior ramus has fifty-five segments! The bristles on the second and third cirri are arranged on the same principle as on the three posterior pair; but from an increase in size and number of the little intermediate bristles between the main pairs, and of those on the lateral rims, the segments, especially the basal ones, of the anterior ramus of the second cirrus, are clothed with thin brushes of bristles; these same bristles, on the posterior ramus of the second, and on both rami of the third cirrus, can hardly be said to form brushes, though longer and more numerous than those on the three posterior pair of cirri.

_Fifth and Sixth Cirri._--These resemble each other, and have their inner or posterior rami in an almost rudimentary condition. In the sixth cirrus (Pl. X, fig. 28) the outer ramus (_a_) has actually sixty-three segments, whereas the rudimentary ramus (_k_) has only eleven, nearly cylindrical segments. These are furnished with extremely minute spines, of which those on the dorsal face are longer than those on the anterior face; the spines on the summit of the terminal segment are the longest; the segments are not half as thick as the normal ones in the outer ramus. The rudimentary ramus is only one seventh part longer than the pedicel which supports both it and the normal ramus. In the fifth cirrus, the rudimentary ramus is rather longer, and has thirteen segments, resembling those in the rudimentary ramus of the sixth. In the fourth cirrus there is no trace of this peculiar structure, the rami being equal in length and strength. The two rudimentary rami on each side are nearly straight, and seem incapable of movement; they project out behind the normal rami, and closely resemble in general appearance, the two caudal appendages; hence this cirripede, at first sight, appears to be six-tailed.

_Pedicels of Cirri._--The pedicel of the first pair is very short; that of the second is the longest; those of the posterior cirri decreasing in length. Upper segments short; lower segments in the second, third and fourth cirri, irregularly and rather thickly clothed with bristles, but in the fifth and sixth cirri, there is a regular double row of main spines, with some minute intermediate ones: hence there is a difference, both in the rami and in the pedicels, between the fourth cirrus and the fifth and sixth, and this is a unique case. On the dorsal surface of the pedicel of the second cirrus, there is a tuft of much feathered fine spines.

_Caudal Appendages._--Each consists of eight much tapering, very thin segments, furnished with a few short simple spines round their upper margins, and with a longer tuft on the terminal short segment; basal segments twice as thick as the middle ones. In length, these caudal appendages equal the pedicels of the sixth pair of cirri, and are a very little shorter than the rudimentary rami of these same cirri.

_General Remarks._--Having examined this species first in the genus, I fully antic.i.p.ated that the very remarkable character of the inner rami of the fifth and sixth cirri being rudimentary, and serving the same function (if any) with the caudal appendages, would have been generic; but this is not the case, for _Alepas cornuta_ cannot be separated from _A. minuta_ without violating a clear natural affinity.

4. ALEPAS TUBULOSA.

Quoy et Gaimard. Voyage de l'Astrolabe, Pl. xciii, fig. 5, 1834.

_A. apertura parva prominente et tubulosa: scutis et prominentiis secundum marginem carinalem, nullis._

Orifice small, tubular, protuberant; capitulum without h.o.r.n.y scuta or projections along the carinal margin.

Animal unknown.

New Zealand, Tolaga Bay. Attached to a living Palinurus.

I have given the above brief character from the plate, and imperfect description in the voyage of the Astrolabe. The small and distinctly tubular orifice, and the smooth carinated edge of the globose capitulum, appear sufficiently to distinguish this species from _A. cornuta_. The colour is stated to have been white with violet tints. Length, two (French) lines.