Dr. J. E. Gray on Chinese Mud- Tortoises. 157 



same purpose, as the Lizards and Snakes. In the ' Annals ' 

 some time ago I showed that the two organs above referred to 

 were not for the purpose which they have generally been 

 considered to serve, but claspers or cramps, like those found in 

 Skates ; only, instead of being exposed as in those fishes, 

 they are retractile under the skin of the body when not required 

 for holding the female. I am now able to show that Tortoises 

 or at least the Mud-Tortoises (Trionychidge), are provided with 

 a well-developed organ for the intromission of the semen, 

 differing in outline in two allied species. 



OSCARIA. 



Skull broad. Nose short, not half the diameter of the orbit. 

 Palatal groove wide, deep, gradually narrowing from the back 

 edge of the internal alveolar process, and rounded in front. 

 Internal nostrils large, roundish, about half the length of the 

 internal alveolar margin, with a deep broad concavity in front. 

 The alveolar process of the lower jaw simple, concave in front, 

 with a slight indication of a longitudinal ridge on the outer 

 side of the middle of the front end, deeply concave and rather 

 widened on each side, with a slightly elevated end and much 

 more elevated outer edge. Tympanic cavity very deep, sub- 

 triangular, with a rounded front edge. 



This genus is very like Trionyx^ but differs in the shape of 

 the palatal groove and in the form of the alveolar surface of 

 the lower jaw. 



The genus Oscar la has the short broad face of Trionyxy 

 and the internal nostrils more anterior than in Isola. The 

 skull of Trionyx LeitJiii is very like the skull of Isola peg u- 

 ensis ; and perhaps this species ought to be referred to the 

 genus Isola, and called Isola Leithii. These species, in the 

 form of the skull, the palatine, in the hinder position of the in- 

 ternal nostrils, and in the form of the alveolar surface of the 

 lower jaw, bear a considerable resemblance to the skull of 

 Aspilus. 



1. Oscaria Swinhoei. PI. V. 



The body oblong, nearly flat, only slightly convex ; upper 

 surface smooth and polished, uniform dark olive-green, with 

 very numerous yellow spots, and a great number of minute 

 yellow circular dots between them, sometimes forming more or 

 less irregular circles round the larger spots. The dots on the 

 fore part of the back, and on the sides and hinder part of the 

 back, are the largest, sometimes confluent into short curved 

 lines, at others forming a ring enclosing a small olive dot. 



