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Show 46 CRUSTACEA. antennre comp1•essed and carinated; ocular pedicles, when erected, entirely exposed. The body is sub-ovoid(l). In the LrniNIA, Leach, The ocular fossulre are very small and nearly orbicular, and the ocular pcdicles are very short, and but very slightly exertile. The second joint of the lateral antennre is cylindrical, and not compress. ed, or but very slightly so. The body is nearly globular, or trian-gular. We will unite the Doclrea and the Egeria of Leach, to his LI· BINI..£, In his Libinire, properly so called( 2), the claws of the males are thicker than the two following feet and almost as long. The length <>f the longest does not exceed twice that of the shell. The claws of the male Doclrea(3) are much shorter than the two following feet. The length of the latter is hardly more than once and a half that of the shell, which is nearly globular and always covered with a brown or blackish down. In the Egerire( 4) the claws are filiform and the hands much elongated and almost linear. The following feet are five or six times longer than the shell. The body is triangular. Having reviewed all the sub-genera of this tribe in which the feet subsequent to the claws are of a simila1• form, and in which the tail, of the females at least, and most generally in both sexes, is composed of seven complete joints or segments, we now pass to those in which it never consists of more than six. The feet are usually long and filiform, as in the last sub-genera. With the exception of the Leptopi, these Crustacea are also removed from the preceding by the form of the third joint of the external foot-jaws. It is proportion· ally narrower, and contracted at base, and the ensuing joint appears to be inserted in the middle of its superior margin, or more externally. The following sub-genus differs from those which succeed to it, in the tail of the males, where we only find three segments. The form of the third joint of the external foot-jaws appears to me the same as in the preceding sub-genera. (1) Cancer araneus, L.; Leach, Malac. Drit., XXI, A; Herbst., XVU, 59;Hyas coarctata, Leach, lb., xxi, ll. (2) Libinia canaliculata, Say, Journ. Acad. Nat. Sc. Philad. vol. I, p. 77, iv, 1; -L. emarginata, Leach, Zool. Misc., cviii. (3) DoclaJa Rissonnii, Leach, Zool. Misc., lxxiv. The Inachua ovis and the T. hybridus, Fab., should be referred to it. (4) Egeriaindica, Leach, Zool. Misc., lxiii; lnachus spinifer, Fab. DECAPODA. 47 LEPTOPus, Lam. Tail of the females composed of but five segments; the body con-vex and feet very long. · But·a single species is known which is part of the collection of' the Museum d'Histoire Naturelle, where it is called Muia longipes. Doctor Leach proposed to designate this genus by the name of Stenopus, a denomination we have not adopted, inasmuch as it is already appropriated to another. That of Leptopus, Lam., is composed of several species, which, the above mentioned one ex, cepted, according to the characters here given, must be excluded from it. If we except some species of Hymenosomre in which the tail pre-sents but four, or at most five, distinct segments, that part of the body consists of six in all the following sub-genera, either in both sexes, or in the males. The third joint of the external foot-jaws is sometimes in the form of an inverted triangle or of a posteriorly narrowed oval, and sometimes in that of a heart. The ensuing joint is inserted in the middle of its superio1· margin, or rather more outwards than inwards. Some of them, such as the three following sub-genera, approach those of which we have just spoken by the almost isometrical, or at least transversal form of the epistoma. The base of the intermediate antennre is but a short distance from the superior margin of the buccal cavity. One of these sub-genera is distinguished from the others by the flatness of the shell, and by the superior extremity of the first joint (free in several) of the lateral antennre, which does not extend be· yond that of the ocular pedicles. Such is the HYMENOSOMA, Leach. The shell is triangular or orbicular( 1 ). The species are generally small and peculiar to the Indian Ocean and coast of Australia. The number of caudal segments varies, but never extends beyond six. In the two following sub-genera, the shell is more or less convex, always triangular and terminated before in a rostrum. The first joint of the lateral antennre, always fixed, forms a ridge or salient line between the fossulre of the intermediate antennre and that of the eyes, and which is prolonged beyond the end of the ocular pedicles. In the (1) Hymenosoma orbicularis, Desmar., Consid., xxvi, 1. |
