OCR Text |
Show 1869.] DR. J. E. GRAY ON THE TORTOISES. 179 superior, often rather close together. Thorax covered with horny plates. Sternum attached to the thorax by a bony symphysis, generally small (compared with the size of the thorax) and cross-like, sometimes large (nearly as big as the thorax); sternal shields variable in number from 7 to 11, never 12. Toes short, spreading, webbed to the claws, shielded above. Skull with a well-developed zygomatic arch, extending from the orbit to the tympanic cavity, leaving a large wide space for the temporal muscles. Palate flat; internal nostrils anterior. Alveolar plate narrow, simple. Iris annular, without any spot on the sides. Section I. CRUCISTERNA. The sternum small, cross-like, narrow at the ends. Head and tail large. Tribe I. CHELYDRAINA. Sternum solid, cross-like, acute before ; sternal plates 10, with a broad one (the displaced abdominal plate) on each side over the produced sides of the sternum. Palate flat; internal nostrils anterior. Alveolar plate flat, rather broad. 1. MACROCHELYS, Gray, P. Z.S. 1855, p. 2W=Gypsochelys, Agassiz ; (skull figured) Gray, Catalogue of Shield Reptiles, t. 38, 39, 40. The alveolar plate very broad. Eyes lateral, distant. 2. CHELYDRA, (skull figured) Gray, Cat. Shield Reptiles, t. 38 & 40. f. 2. Alveolar plate moderate. Eyes superior, rather close together. Sta urotypus salvin ii. |