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Show 28 CHUSTACEA.. elongated, salient and composed of many joints, but very hairy as well as the claws; the latter strong, and with compressed hands. The third joint of the foot-jaws sensibly narrowed above, resembling an obtuse or rounded tooth; conical tarsi, and the ocular pcdicles of the ordinary size. The tail is longer than in the preceding Crus-tacea. Two species have been described( 1 ). One from the coast of England, of a sub-orbicular form, and the other from that of France, Mediterranean as well as Oceanic. The THIA, Leach, Approaches Atelecyclus in the lateral antennre, in the direction of the fossulre in which the intermediaries are placed, in the form of the third joint of the external foot-jaws, and in the sub-orbicular shell; but the eyes, together with the pedicles, are extremely small and scarcely salient. The tarsi are strongly compressed and subelliptical. The front is arcuated, rounded, and without any marked dentations. The pectoral space between the feet is very narrow, and of the same breadth throughout. The claws are much weaker in proportion. The shell is smooth, and in 5ome respects the Thire approach the Leucosire and the Corystes. The type(2) of this subgenus, whose habitat was unknown, has been discovered by Milne Edwards in the sandy shores of the Mediterranean, near Naples. Risso-Journ. de Phys., 1822, p. 251,-described a second, dedicated to M. de Blainville, which he found in the river at Nice. The MuRsiA, Leach(3), Of' which but a single species is known, and which is peculiar to that part of the Ocean which bounds the southern extremity of Afri· ca, approaches the Matutre and several Portuni, in the long spine with which each side of the shell is armed posteriorly; it also appt·oximates to the true Crabs in the form of the shell and of the external foot-jaws, with this difference, that their third joint forms an elongated square, narrowed and obliquely truncated at its supe· rior extremity; but, as in the Calappre and Hepati, the hands are strongly compressed above, having a sharp and dentated edge, re· sembling a crest(4). (1) Se~ Co~sid. Gener. sur la Classe des Crust., Desmar., p. 88, 89. (2) Tlua pohta, Leach, Zool. Miscell. ciii. (3) This name must be changed to avoid confounding the di'.lision with that of Nur&ia, another subgenus. (4) Desmarest, Comid. Gener., &c., IX, 3. DECAPOD A. 29 HEPATus, Latr. The Hepati have a considerable affinity with the t~ue Crabs in the · dened form of their shell, and the shortness of their lateral anten- Wl • h . d nre, approaching the Mursire and Calappre m t eir . con~pr~s~e hands, the upper edge of which resembles a crest; but the third .Jomt of their external foot-jaws forms an elongated, narrow, and pomted triangle, without any apparent emargination, a character also observed in the Matutre and Leucosi::e. The species( 1) which served as the type of this division was confounded by Fabricius with the Calapp. It is as large as an ordinary Pagarus. The shell is yellowish, dotted with red, and the margins finely and un~qually crenulated. The eyes are small and approximated, . and the feet are traversed hy red bands. Although the tail of the male has but five complete segments, the traces of two others may still be discovered on the sides. This species is common at the Antilles. In 0 u1• third section or that of the QuADRILATERA, the shell is nearly square or heart-shaped, the front generally prolonged, inflected or mucli inclined, and forming a sort .of clypeus. There are seven segments, distinctly marked across their whole breadth, in the tail of both sexes. The antennre are usually very short. The eyes of most of them are fixed on long or stout pedicles. Several live habitually on land, inhabiting holes excavated by them- . selves; others frequent fresh water streams. They move with great swiftness(2). A fit·st division will comprise those in which the fourth joint of the external foot-jaws is inserted at the superior internal extremity of the preceding one, either in a short, truncated projection, or in a sinus of the inner margin. They approach nearest to the Crabs proper. The shell of some is nearly square, or a trapezium, but not trans-verse, or almost in the form of a truncated heart. The ocular pedicles are short, and inserted either near the lateral and anterior angles of the shell, or more internally, but always 'at a considerable distance from the middle of the ft·ont. Here comes the (1) Hepatus fasciatus, Latr.; Desmar., Consider., IX, 2;-Calappa angustata, Fabr.; Cancer princeps, Bose.; Herbst., xxxvii, 2. See also his Cancer armadillus, VI, 42, 43. (2) 1 consider them, with respect to their habits and some of the characters of their organization, as being the furthest removed from the other Decapoda; they should be placed at one of the extremities of that order. |
