328 Dr. J. E. Gray on the Mud-Tortoises of India. 



same species ; whilst a Central-African tortoise, Aspidonectes 

 aspilusj has been separated from Tyrse nilotica because the 

 individual had slightly differently developed sternal callosities, 

 whereas the examination of the jaws shows that they are the 

 same species. 



The study of the jaws at various ages has shown that the 

 form of the alveolar surface is the same in the young as in the 

 adult, and therefore furnishes a very excellent character for di- 

 stinguishing the species ; and if one had skulls of all the species 

 in the collection, they would no doubt afford the characters of 

 the various kinds, and also the best arrangement of them into 

 groups. But, unfortunately, that is not the case, and we are 

 obliged to do the best we can under the circumstances. Un- 

 fortunately, too, the skulls cannot be extracted from the stuffed 

 specimens without destroying them ; and it is always difficult 

 to be certain that the skulls and skeletons that you receive 

 belong to the species they are said to represent ; for the char- 

 acters by which the species are distinguished in their perfect 

 state have been destroyed. Every care has been taken to pre- 

 vent an error of this kind ; and in general the characters of the 

 genera have been taken from the examination of the head in 

 the perfect animal, and of the skulls extracted from duplicate 

 specimens. It is much to be regretted that the Indian zoolo- 

 gists do not study the numerous Asiatic species and give us the 

 result of their examination, considering that there are only two 

 Indian zoologists in modern times who have paid the slightest 

 attention to these animals, and they have not yet learned the 

 elements of herpetology. Thus Mr. Theobald and Dr. Ander- 

 son have described two most different animals under the name 

 of Trionyx Phayrei^ and have described them in such an in- 

 correct and imperfect manner that it is impossible to make out 

 to what species, or section, or genus either of them is refer- 

 able. 



The receipt of some additional specimens of mud-tortoises 

 and their skulls required that they should be determined ; and 

 to do this I have been induced to study and revise what I had 

 formerly written : as our materials are so imperfect, from the 

 Indian collectors not sending home specimens, it is a matter of 

 great difficulty. We know far less of the tortoises of our 

 Indian possessions than we do of those of almost any other part 

 of the world. Experience has shown me that the most reliable 

 character for the distinction and arrangement of the tortoises, 

 and especially of the mud-tortoises, is to be obtained by tlie 

 study of the skulls ; I have therefore been particular in col- 

 lecting them, and (where it could be done without injury) 

 have had the skulls removed from several of the specimens. 



