Mandibles with four teeth; segments of the three posterior cirri with eight pair of main spines.
_Hab._--Madeira; attached to a rare Brachyourous Crab, discovered by the Rev R. T. Lowe. Very rare.
_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.
_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 p.r.o.ngs, 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 p.r.o.ngs 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 p.r.o.ng 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 lamellae.
_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. Maxillae 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 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 fere dimidia; duorum segmentorum junctione calcarea: tergorum prominentiis marginalibus inaequalibus quinque: carina deorsum in parvo calyce lunato terminata._
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.
Maxillae with the inferior part of edge much upraised.
Hab. unknown; a.s.sociated with _Scalpellum rutilum_, apparently attached to a h.o.r.n.y coralline. British Museum.
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.
_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 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.
_Maxillae_ 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 Maxillae_, 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 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 maxillae projecting.
OXYNASPIS.[33] _Gen. Nov._ Pl. III.
_Valvae 5, approximatae: scutorum umbones in medio marginis occludentis positi: carina rectangule flexa, sursum 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.
[33] From [Greek: oxuno], to sharpen, and [Greek: aspis], a shield or scutum.
Mandibles with four teeth; maxillae 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.
Attached to h.o.r.n.y corallines.
I have most unwillingly inst.i.tuted this genus; but it will be seen by the following description, that the one known species could not have been introduced into Lepas or Paecilasma, 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 Paecilasma; but taking the entire animal, its 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 ident.i.ty 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 Paecilasma 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 Paecilasma to Lepas.
1. OXYNASPIS CELATA. Pl. III, fig. 1.
Madeira; attached in numbers to an Antipathes; Rev. R. T. Lowe.
Mus., Hanc.o.c.k.
_General Appearance._--The capitulum is rather thin, and broad in proportion to its length; it seems always entirely covered by the h.o.r.n.y muricated bark of the Antipathes, and hence externally is coloured rich brown and covered with little h.o.r.n.y 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 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.