786 EEPTILIA. 



Genus Trionyx, GeofP. 

 TmoNYX PEGUENSis, Gray. Plates LXX, — LXXIII, 



Trionyx peguensis, Gray, Suppl. Cat. Shd. Rept._, 1870, p. 99^ Theobald, Descr. Cat. Eept., Brit, 

 ind. (CalcuJ^ta), 1876, p. 31. 



Isola peguensis, Gray, Proc. Zool. Soc, 1873, p. 31. 



The specimens of Trionyx collected by Mr. Theobald in Pegu and Arracan, 

 and which found their way to the British Museum, were three in number, as far as 

 I have been able to make out by an inspection of the registers in which they 

 are entered and of the specimens themselves. There is a young Trionyx in 

 alcohol, the type of T. formosus^ and the skull of which was afterwards ex- 

 tracted ; the skull of the type of T. phayrei^ the shell of which was presented 

 by Theobald to the Bristol Museum^; and the head of an adult in spirit,'' the type 

 of T. pegue7isis, and the skull of which was afterwards figured under the name of 

 Isola peguensis. 



Theobald mentions that only two skulls of Trionyx (exclusive of young animals 

 in spirit) passed from his hands into the British Museum, either by gift or purchase, 

 " a head of T. stellatusT and second, " the skull of my type of T, phayrei.'" This 

 is confirmed by the Hand List of Shield Pi^ep tiles. 



The history of these specimens is noteworthy. The young animal in alcohol 

 was described in 1869 as T. formosiis,^ and in 1872 as Nilsonia formosa,^ but 

 at this latter date Dr. Gray contrasts the skull of the young animal which had 

 been removed from the specimen, with an adult skull which he received from 

 G. Palconer, Esq.,^ one of the executors of the late Dr. Hugh Palconer. This adult 

 skull has been since figured,^ and we are thus enabled to judge of its true nature. 

 After a careful consideration of the figure, I do not hesitate to pronounce it to be 

 the skull of a Gangetic species, viz., T. hurum^ distinguished from T. Gangeticus by 

 its antero-posteriorly long symphysis without a median ridge, and to be the skull of 

 the fresh-water tiirtle which has been described under the names of T. sewaare^^ 

 T. ocellatus^^ and T. huchanani,^^ all of wdiich yield similar skulls, quite distinct 

 from the young skull of T.formosus. The skull of T. phayrei was first apparently 



1 Hand List SM. Eept., B. M., 1873 p. 77. 



2 1. c, p. 80. 



3 Obs. on Ind. and Burm. Trionyx, Theobald, Cal. 1873, p. 8. 



4 Hand List Shd. Kept., p. 80. 



5 Proc. Zool. Soc, 1869, p. 217, Plate xv, %. 1; Suppl. Cat. Shd. Eept., 1870, p. 99. 



6 Ann. and Mag. Nat. Hist., vol. x, p. 332, 4th Ser., 1872. 



7 1. c, p. 332. 



8 Proc. Zool. Soc, 1873, p. 46, fig. 2. 



9 Syn. Rapt., 1831, p. 47, Tab. x; 111. Ind. Zool. vol. ii, 1833, t. 16. 



10 Gray, Ann. and Mag. Nat. Hist., vol. x, 1872, p. 336 ; Proc. Zool. Soc, 1873, p. 50 : Theobald, Proc. As. Soc, 

 Bengal, 1875, p. 172. 



" Ann. and Mag. Nat. Hist., vol. x. 1872, p. 337; Proc Zool. Soc, 1873, p. 51 ; Theobald, Proc As. Soc, Bengal, 



1875, p. 174. 

 12 Proc As. Soc, Bengal, 1874, p. 78. ' 



