220 Dr. Anderson on Trlonyx gangcticus, Cavier. 



p. 97 in tlic Supplement to the latter work, is not the skull 

 of that species. 



The confusion that exists in Dr. Gray's Catalogues regarding 

 the foregoing species {T. hurum) and his so-called Trionyx 

 javmiicus, Schweigger, MS., ' Illustrations of Indian Zoology,' 

 {T.javanicus, Geoff.) ' Synopsis Reptilinm,' p. 48, and ' Cat. 

 Shield Kept.' p. 67, and Potamochelys stellata, Geoff., ' Suppl. 

 Cat. Shield Rept.' p. 104, is alone explicable on the justifiable 

 supposition that Dr. Gray is more anxious to catalogue the 

 specimens under his charge than to work out their natural 

 affinities by a careful consideration of the characters of the 

 materials at his disposal. It would be well if Dr. Gray would 

 carefully ponder the admirable advice which was so ably ten- 

 dered to him by M. Brunner de Wattenwyl*, and remember 

 that " les esp^ces sont des entites de la nature dont 1' observa- 

 tion est du domaine de la philosophic." 



The pernicious practice of creating new genera on characters 

 derived exclusively from single skulls or from drawings of 

 skulls Avithout any knowledge whatever of the animals that 

 yielded them, has resulted in this, that we find animals de- 

 scribed by Dr. Gray in his Catalogues with their skulls and 

 tails allocated in widely apart genera. The confused maze of 

 synonyms which this practice has elaborated can be better 

 imagined than described. 



The facts connected with the two Gangetic mud-tortoises 

 are these : — Dr. Gray's figure in the ' Illustrations of Indian 

 Zoology,' bearing the name Trionyx javanicus^ Schweigger, 

 ]\IS., represents t!ie most prevalent species. Its skull is iden- 

 tical with the skull figured by Dr. Gray at pi. xlii. fig. 1 of 

 his ' Catalogue of Shield Heptiles,' and which is there correctly 

 named Trionyx gangeticus. This skull, however, is referred 

 by Dr. Gray to the other species of Gangetic mud-tortoises, 

 which was originally described by him in his ' Synopsis Rep- 

 tilium,' p. 47, under the name Trionyx hururn^ but Avhich in 

 his ' Suppl. to the Cat. of Shield Eept.' ]). 97, is reproduced 

 as T. gangeticus^ Cuvier. This species [T. hurion), however, 

 does not yield a skull like the skull figured by Cuvier as T. 

 gangeticus ; but if Dr. Gray will turn to pi. xlii. fig. 2 of his 

 ' Cat. of Shield Kept.' he will find a skull figured, but without 

 . a name, which is very closely allied to the skull of T. hunnn. 

 The differences that exist between the skulls there figured in- 

 dicate those that exist between Trionyx gangetic2cs and Trionyx 

 hurum. But, although it is impossible to separate generically 

 the skulls figured on that ])late. Dr. Gray makes the unguarded 

 statement that the two mud-tortoises of the Ganges, in question^ 

 * Rev. et Mag. de Zoologie, Mars 1870. 



