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Show 58 CUUSTACEA. BxnGus, Leach, · The tail is tolerably solid, subot·bicular, and is furnished beneath with two rows of laminiform appendages. The fourth feet are but a little smaller than the two preceding ones; the two last are ~olded and concealed theit· extremities being received into a depresswn at the bottom of the thorax; the fingers at the extremity, as well as those of the penultimate pair, are hairy or spino~s. ~r~1e claws except. ed all the feet are visibly separated at theu· ongm. The thorax ha~ the figure of a reversed heart, and is pointed an~erio:ly · It appears that ft·om their size, the form of t~e1r. tatl, and the more solid consistence of their teguments, the Btrgt are unable to shelter themselves in shells. They must retreat to holes, or fissures in the rocks. The best known species, Cancer latro, L., Herbst. XXIV; Rumph., Mus., IV; Seba, Thes., III, xxi, 1, 2, according to the Indians, feeds on cocoa-nuts which it obtains during its noctur· nal excursions for that purpose( 1 ). In the others, or the PAGuRus, Fab., The last four feet are much shorter than the preceding ones, and the forceps are covered with gt·anules. The tail is soft, long, cylin· drical, narrowed near the extremity, and has usually but a single row of filiform oviferous appendages. The thorax is ovoid or oblong. With the exception of some species domiciliated in sponges, Ser· pulre and Alcyonii, they all inhabit univalve shells, whose aperture they close with their anterior claws, and most frequently with one of their fingers, which is usually larger than the other. It is asserted that the female spawns twice or thrice in the year. Some species, CJENOBITA, Latr.; distinguished from the others by their projecting antennre, of which the mediate are neady as long as the external or lateral, and are furnished with elongated filaments, whose thorax is ovoido-conical, narrow, elongated, strongly com· pressed on the side, with the anterior cephalic pot·tion shaped like a heart, establish their domicil in terrestrial shells on rocks near the sea, whence, at the approach of danger, they roll down with them(2). (1) Pagurua laticauda, Cuv., Regn., Anim., IV, xii, 2; Desmar., Consid~r., P· 180, from the Isle of France. Very curious facts relating to the anatomy of the preceding species have been published by M. Geoffroy Saint-Hilaire, from which however we do not draw similar conclusions. (2) Pagurua clypeatua, Fab.; Herbst., xii, 2. DECAPOD A. 59 The true Paguri-PAGURus, Latr.-on the contrary, have the mediate antennre curved, much shorter than the lateral ones, with the two filaments short, the superior forming an elongated or subulated cone: the anterior division of the thorax is square, or forms arevers~ d and curvilinear triangle. They inhabit marine shells. The /Jer~Jnit,-Cancer Bernhardus, L., Herbst., XXII, 6; Pagurus streblonyx, Leach, Malac. Brit., XXVI, 1-4,-is of a mean size. Its two claws are bristled with spines, with the forceps almost in the shape of a heart, the right one being the largest. The last joints of the ensuing feet are also spinous. It is very common in European seas. A second but fossil species, the Pagure de Faujas,-Desmar., Hist. Nat. des Crust. Foss., .xi, 2,-is closely allied to it. A third species, the Pagurus angulatus, Risso, Crust. de :Nice, I, 8; Dcsmar., Consider., XXX, 1, is remarkable for its forceps, which are strongly sulcated with longitudinal ridges. The right one is the largest( 1 ). A fourth from the same sea is removed from the preceding by several characters, and merits the distinction of forming a separate subgenus, the PRoPHYLAX, Latr. The tail, with the exception of the superior surface of the three last segments, instead of being soft and arcuated and having but a single range of oviferous filaments, is covered with a coriaceous tegumeut, is straight, and is only curved beneath at its extremity; its inferior surface presents a groove and two rows of false feet. The body also is linear, and the two lateral appendages of the end of the tail are almost equal, the larger division being foliaceous and ciliated. The last four feet are slightly granulated at their extremity, and appear to be terminated by a single finger, or at least are not distinctly bifid. Perhaps we should refer to this division those Paguri which inhabit the Serpulre, and Alcyonii, such as the Pagurus tubularius, Fab. In all the following Macroura, the two posterior feet at most are smaller than the preceding ones. Most generally the sub-caudal false feet form five pairs. The teguments are always cru·staceous. The lateral fins of the penultimate segment of the tail, and its last, form a common one at·ranged like a fan. The two subsequent sections possess a common character, which (1) }"or the other species see the article Pagure, Encyc. M~thod.; the Atlas d'Hist. Nat., of the same work; Desmarest, Consid~r. Gener. sur Ia Classe des Crust.; the plates of the Voy. de Freycinet. We should observe that in the figure of the Cancer megiatoa, Herbst., LXI, 1, the tail is false; this arises from the fact that the tail was wanting in the individual from which the drawing was made, the arti$t supplying it by copying the fin-tail of an ordinary Macroura. |
