_Rostrum_, small, much curled inwards; the basal margin is much hollowed out; the inner surface is broadly triangular, more than twice as wide as high, and about one fourth of the entire length of the valve. The remaining valves, about 26 in number, do not correspond on the opposite sides of the same individual, they are exceedingly small, with the sub-carina, sub-rostrum, and three pairs of latera a trifle larger than the lower latera, which are generally arranged in two whorls. In shape all the latera are nearly alike; they consist of flattened styles, with their inner surfaces transversely oval, and more or less elongated, the larger ones being most elongated.
_Peduncle_, broad, barely as long as the capitulum. The calcareous scales are irregularly shaped, minute, elongated and pointed, placed in separate transverse rows, and crowded together in each row. Only the scales in the uppermost row grow regularly; but some of the lower scales continue to be added to irregularly, and hence are the largest. On the other hand, the lower part of the peduncle, from the first formed scales having been worn away, is often quite naked. From this cause, and from the continued and irregular growth of some of the lower scales, the rows in this part of the peduncle, generally become irregular. The surface of attachment is broad.
In a half-grown specimen, with a capitulum only 3/10ths of an inch long, all the lower valves were considerably larger in proportion to the scuta, terga, and carina, than in full-grown individuals.
_Size and Colours._--Length of capitulum in the largest specimen, 7/10ths of an inch; breadth, slightly exceeding the length. Colours after having been long in spirits--upper part of sack, thorax, pedicels of cirri, and p.e.n.i.s, clouded with fine purple; cirri banded with the same; exterior convex surface of the outer and inner maxillae and palpi dark purple; prosoma yellow. The membrane of the peduncle and of the capitulum is dirty yellow, with bands of purple between some of the valves.
_Filamentary Appendages_, none. Ovigerous fraena placed near the middle of the basal margin of the scuta; small, semi-oval, with an elliptical ring of bead-like glands; glands seated on long footstalks.
_Mouth._--Labrum far produced towards the adductor muscle; upper part highly bullate, nearly equalling the longitudinal diameter of the rest of the mouth, and very slightly overhanging the lower part; crest with very minute bead-like teeth.
_Palpi_, with their inner margins considerably excised, most thickly clothed with spines.
_Mandibles_, with three strong teeth, two unequal-sized small teeth being placed between the first and second, thus making five altogether; inferior angle broad, pectinated.
_Maxillae_, with its edge broad, straight, bearing about twenty pairs of spines, shorter than the large upper spines.
_Outer Maxillae_, with the bristles in front, continuous, and without any notch; exterior surface with a prominence clothed with long spines.
Olfactory orifices slightly prominent.
_Cirri._--First cirrus placed near to the second; posterior cirri not much elongated, with their segments slightly protuberant, bearing four pairs of spines, of which the lower pair is small; spines slightly serrated. In the lower segments, these spines are exceedingly unequal in length, the inner spines on both rami, not being above one fourth of the length of the outer corresponding spine in each pair. The tufts intermediate between these pairs, are not very large: on the lateral upper rims there are some strong, short spines: dorsal tufts with short, thick spines. First cirrus about three fourths as long as the second cirrus, with numerous tapering segments, three or four of the lower ones being thick and protuberant: in the first cirrus there are eleven segments, and in the sixth cirrus, seventeen. Second cirrus, with the anterior ramus slightly thicker than the posterior ramus: a few of the basal segments of both rami are protuberant, and thickly clothed with spines. In the third cirrus, the two rami are nearly equally thick, with some of the basal segments in both clothed, like a brush, with spines.
In these brushes on the first, second, and third cirri, most of the spines are doubly toothed, each tooth being simply conical.
_Caudal Appendages_, small, much flattened, straight on the exterior side, and curved on the inner side, with a row of short, rather thick spines on the crest, and a few on the exterior margin.
The _Affinities_ of this species will be given under the head of the following, _P. sertus_.
6. POLLICIPES SERTUS. Pl. VII, fig. 5.
_P. capitulo valvarum uno aut pluribus sub-rostro verticillis instructo: laterum pari superiore vix inferioribus longiore: membrana valvas tegente (post desiccationem) fusco rufescente obscuro: rostro dimidiam carinae longitudinem aequante, superficiei internae alt.i.tudine lat.i.tudinem plus duplo superante: pedunculi squamis inaequalibus, non symmetricis: verticillis longiuscule distantibus._
Capitulum with one or more whorls of valves under the rostrum: upper pair of latera only slightly larger than the lower latera: membrane covering the valves (when dried) dark reddish-brown: rostrum half as long as the carina, with its inner surface more than twice as high as broad: scales of peduncle of unequal sizes, unsymmetrically arranged in rather distant whorls.
Maxillae with two tufts of fine bristles, separated by larger spines: caudal appendages uniarticulate: filamentary appendages none.
New Zealand; Mus. c.u.ming.
_Capitulum_, much flattened, broad, sub-triangular. Valves exceedingly various in number; in the largest specimen with a capitulum 8/10ths of an inch high, and 9/10ths of an inch wide, there were only thirty-one valves, and these formed only a single whorl under the carina and rostrum; whereas, in another specimen, which was barely 6/10ths of an inch in length, there were fifty-two valves, and these formed two or three distinct whorls under the carina. Scuta, terga, carina, and rostrum, much larger than the other valves. All are moderately thick, placed rather distant from each other, covered with thick membrane which abounds with tubuli, arranged in rows; surface apparently smooth, but with a very high power, extremely minute spines can be seen at the extremities of almost all the tubuli. Little bunches of reddish fibrous matter are imbedded in the membrane, like tufts of sea-weed floating in water.
_Scuta_, triangular, basal margin curved, protuberant; the upper part of the tergo-lateral margin is, also, slightly protuberant.
_Terga_, large, oval, basal angle broad, square; lower part of carinal margin straight, upper part narrowed in; the apex is covered with membrane and projects freely.
_Carina_, triangular, internally deeply concave, either straight, and with the apex free, or inwardly and considerably curved; basal margin nearly straight.
_Rostrum_, about half the length of the carina; either straight or inwardly curved; it projects freely for full half its length; inner growing surface triangular, more than twice as high as wide; basal margin very slightly hollowed out. The _sub-carina_ and _sub-rostrum_ are larger than the largest of the latera; their inner surfaces are transversely elongated, rounded at both ends, and slightly concave; externally they are pointed, and project outwards; sometimes the sub-carina, and sometimes the sub-rostrum is the largest.
_Latera_, small, with their inner surfaces transversely elongated, the larger being the most elongated. Externally they are ac.u.minated, and directed upwards; they project but very little beyond the thick membrane in which they are imbedded. Neither the number, size, nor shape of the latera agree on opposite sides of the same individual; and it would appear that, occasionally, some of them cease to grow, and disappear. In the large specimen with only thirty-one valves, the three pairs of latera, corresponding to the upper, rostral, and carinal latera in Scalpellum, were larger in a marked manner than the others; but in the specimen with fifty-four valves, this could hardly be said to be the case. In this latter specimen, some of the valves in the lowermost whorl were exceedingly minute.
_Peduncle_, broad, about as long as the capitulum; surface of attachment wide; calcareous scales minute, placed in transverse rows, which become less and less regular in the lower part. The scales do not stand very close together; they are of unequal sizes and irregular outline; generally spindle-shaped; calcareous matter is added regularly only to the scales in the uppermost row, and irregularly to some of the lower scales. The latter, consequently, are the largest, and often much elongated; they are sometimes of singular and irregular shapes.
_Colour._--The membrane covering the valves and forming the peduncle, (after having been long kept dry, and not having been in spirits,) is dark reddish chocolate-brown; corium of sack dark purple; cirri banded with dark purplish-brown, with the lower parts of the trophi similarly coloured.
_Filamentary Appendages_, none, but on the prosoma there are scattered some small papillae, which are roughened by finely spinose scales, like combs; these papillae certainly seem to represent the filaments in _Pollicipes cornucopia_ and its two allies.
_Ovigerous Fraena_, seated in the same position as in _P. spinosus_, but rather longer, with an elliptical _tuft_ of glands on the crest.
_Mouth_, not placed far from the adductor muscle.
_Labrum_, moderately bullate, with the upper part not overhanging; no teeth on the crest. _Palpi_, short, broad, blunt.
_Mandibles_, with three main teeth, with either one or two smaller teeth inserted between the first and second, making four or five altogether; inferior angle rather narrow, pectinated with long and fine spines.
_Maxillae_, rather broad, with two long upper spines; beneath which there is a very small prominence bearing a minute tuft of fine bristles; beneath this, there are eleven pairs of rather long and strong spines; and the inferior angle is formed by a rather broad, upraised, and obliquely rounded prominence, bearing a broad tuft of fine spines.
_Outer Maxillae_, with the inner surface continuously clothed with short spines; exteriorly there is a slight prominence with long hirsute spines.
_Olfactory Orifices_ barely prominent.
_Cirri._--First pair placed near the second; the segments of the three posterior pairs are slightly protuberant, and bear three or four pairs of finely serrated spines; intermediate tufts long, the middle spines being the longest; spines on the upper lateral edges long and strong; dorsal tufts rather short. _First cirrus_, long, multiarticulate, having fourteen or fifteen segments, whilst the sixth cirrus had nineteen segments; rami unequal in length by about two segments; basal segments protuberant brush-like. _Second_ and _third cirri_ with five basal segments of both rami protuberant and brush-like; but the anterior rami in both cirri are broader than the posterior rami. Spines on the protuberant segments of both rami of both cirri, coa.r.s.ely and doubly pectinated.
_Caudal Appendages_ (Pl. X, fig. 19), minute, uniarticulate, club-shaped, with the enlarged ends directed inwards, or towards each other; summits sparingly clothed with very short spines.
_p.e.n.i.s_, small.
_Affinities._--This species makes a very close approach in the general form and relative sizes of all the valves, and in the variability of the number of the whorls, to _P. spinosus_; there is a still closer and more important resemblance, in the inequality and manner of growth of the calcareous scales on the peduncle. These species differ, in the colour of the membrane covering the valves, and in the greater development of both rostrum and sub-rostrum in _P. sertus_. The rostrum of the latter is longer than half the length of the carina, and its inner surface is more than twice as high as wide; and the sub-rostrum is twice as large as any of the latera,--all points of difference from P. _spinosus_.
In the characters of the mandibles, and more especially of the outer maxillae; in the length of the first pair of cirri; in both rami of the second and third cirri having their basal segments brush-like, with pectinated spines; and in the shape of the caudal appendages, there is a close relationship to _P. spinosus_, and through this species to _Scalpellum villosum_. In the little prominence of the olfactory orifices, P. _sertus_ differs from most of the allied forms, excepting _P. spinosus_. In the maxillae having two prominences bearing fine tufts of bristles, in the roughened k.n.o.bs on the prosoma, and in the presence, in some individuals, of two or three whorls of valves under the carina and rostrum, there is a marked tendency in _P. sertus_ to approach _P.
cornucopia_, _P. elegans_, and _P. polymerus_.
_Genus_--LITHOTRYA. Pl. VIII, IX.
LITHOTRYA. _G. B. Sowerby._ Genera of Sh.e.l.ls, April 1822.
LITHOLEPAS. _De Blainville._ Dict. des Scienc. Nat., 1824.
ABSIA.[65] _Leach._ Zoological Journal, vol. ii, July 1825.
BRISNaeUS et CONCHOTRYA. _J. E. Gray._ Annals of Philosophy, vol.
x, (new series,) August 1825.
LEPAS. _Gmelin._ Systema Naturae, 1789.
ANATIPA. _Quoy_ et _Gaimard_. Voyage de l"Astrolabe, 1832.
[65] The description of Absia is so inaccurate, that I should not have recognised it, had not the _Lithotrya Nicobarica_, in a bottle in the British Museum, borne this name.