OCR Text |
Show 714 DR. J. E. GRAY ON THE DERM ATEM YD/E. [Nov. 1, I believe that the genus Dermatemys will be the type of a new family, which may be called Dermatemydce, and thus characterized. Fam. DERMATEMYD*. Skull:-the head moderate, rather high, covered with a thin, soft, continuous skin ; temples with small polygonal shields; zygomatic arch distinct ; tympanum large, covered with a granular skin. Eyes lateral; iris circular, narrow. Nose produced, conical; nostrils apical, flesh-coloured. Beak strong: upper beak coloured like the skin of the head, hard ; lower beak strong, hooked in front. Alveolar surface of the upper jaw with a triangular ridge parallel to the outer edge of the jaw, and with a short separate transverse ridge in front, separated from the front of the beak by a deep pit. Lower jaw with three or five strong teeth in front, which fit into the pit in front of the upper jaw. The alveolar surface flat, with a deep central groove along each side. Chin not bearded. Thorax oblong, the hinder edge expanded and slightly reflexed, covered with very thin, membranaceous shields, which have the areola in the young animals on the hinder margin. Sternum flat, united to the margin by a bony symphysis, rounded in front and notched behind. Sternal shields twelve, very thin, membranaceous. The gular plates small, triangular, sometimes united into a single plate, with three additional intramarginal plates on the suture between the triangular axillary and the band-like inguinal plates between the small abdominal and marginal plates. The cavity of the shell scarcely contracted at the opening. The legs short, fringed on the outer side, granular. Toes weak, broadly webbed. Tail short, thick, angular, with ridges of spines and a horny tip. The head of these animals has much the appearance of Batagur, and the shell has a certain resemblance to those of that genus. The form of the sternum might be mistaken for that of an Hy-draspis ; but it will be found that what looks like the intergular plate is, in fact, the small gular plates, which are sometimes separate, but usually united together, there being only six pairs of plates, without any anterior additional one. Synopsis of the Genera. 1. D E R M A T E M Y S . Crown flat. Vertebral shields elongate, the first the shortest. The gular plates separate or united. 2. C H L O R E M Y S . Crown convex. Dorsal shields wider than long. The gular plates united. 1. DERMATEMYS. Head flat above, rather keeled on the sides. The crown narrow and produced behind. Temples with small polygonal shields. Thorax convex. Nuchal shield distinct, short. First vertebral plate as broad as long ; second, third, and fourth longer than broad ; the fifth narrow and produced in front, broad behind. Gular plates |