38 CHELONIA. 



rounded posteriorly; sternum truncated in front. Small portions between the extremities 

 of the ribs appear to remain cartilaginous during the whole lifetime of the animal. 



Plates. — The whole carapace is remarkably smooth and polished. Nuchal plate sub- 

 quadrangular, much broader than long, and broader posteriorly than anteriorly. The four 

 anterior vertebrals subquadrangular, nearly as broad as long ; the fifth hexagonal ; none of 

 them have any trace of a ridge. Caudal plates square, separated by a suture, without notch 

 behind ; hind margin not serrated, lateral margin sharpish posteriorly and obtuse anteriorly. 

 Gulars twice as broad as long, the length of their suture being two-sevenths of the suture 

 between the postgulars. Postgulars longer than broad, as long as the pectorals, but shorter 

 than the abdominals and prseanals. Anals quadrangular, their suture being equal in length 

 to their posterior margins, which meet at a very obtuse angle. 



Head covered mth undivided skin ; snout rather pointed, nose turned upwards ; upper 

 jaw denticulated. Tail rather shorter than tlie head. 



Feet. — Fingers and toes completely webbed ; four rather weak claws anteriorly and 

 iwsteriorly. Forearm and lower leg -with very narrow, not imbricate, transverse scutes. 



The colour is a uniform brown in preserved specimens. 



This description is taken from an adult specimen. A young individual, 2^ inches long 

 {Tetraonyx affinis, part., Cant.), has the shell orbicular, much depressed, with an obtuse keel 

 along the vertebrals ; it is not serrated posteriorly, and only the lateral plates project slightly. 

 The skin of the head is rugose. The umbilical cicatrix on the sternum is still visible. 



Dr. Cantor says, in his description of Tetraonyx affinis, that he had three small specimens 

 for examination ; two of them were sent by him to the Collection of the East India Company, 

 whence they have been transferred to the British Museum. They still have the original 

 labels attached to them ; but Dr. Cantor was much mistaken in considering them as identical, 

 the one being a young B. baska, the other a young individual of a species for which we 

 retain Cantor's name. As it is evident that he himself considered the specimen with four 

 claws, of which, besides, he gives the dimensions, as the type of his T. affinis, this name 

 ought to be considered as synonymous with £. baska. We have figured the young £. baska, 

 from Cantor's collection, on Plate III. figs. B, B', of the natural size. 



This fine species, the shell of which attains to a length of 20 inches, is thoroughly aquatic ' 

 in its habits ; it is found in the Ganges and Irawaddy, and probably in numerous other rivers 

 of the Indian continent. Mr. Blyth says that it abounds at the mouth of the Hoogly, and 

 that great numbers are brouglit to Calcutta, where they are eaten by particular castes of 

 Hindoos, and are even kept for sale in tanks. The specimen from Dr. Cantor's collection 

 appears to have been caught in the sea off Pinang, " with a small hook baited with a 

 shrimp." 



