78 W. Theobald— 0;^ Indian and Burmese species of Trionyx. [March, 



History for 1871, Dr. Gray commits a serious error in stating that this 

 species never exhibits the " semicircular bone in the front of the sternum, 

 covered with a lunate callosity," for such will, I think, be found in all aged 

 specimens of Tr. gangeticus, though not developed till the animal has nearly 

 attained its full size. Dr. Gray's views seem in this matter to run in ex- 

 tremes. In his Catalogue of Tortoises, &c ., dated 1844, at page 46, he 

 writes : — " The sternal callosities appear and increase in size as the animal 

 increases in age, hence they do not afford specific, much less generic, charac- 

 ters." So far from this being the case, the characters of the osseous plates of 

 the sternum would seem to be one of our best means for diagnosing the differ- 

 ent species of TrionycJiidce, without accepting the later view of Dr. Gray and 

 making them of generic value, by strictly following which method we should 

 risk placing the young animal in oiie genus, the mature animal in another, 

 and the aged and patriarchal member of his race, in a third ! 



Tiiis lunate callosity is also found in Tr. BJiayrei, Th., and equally well 

 developed in the species identified by Dr. Anderson as Tr. hurum. This 

 is well exemplified in the skeleton of a superb male in the Imperial Museum 

 and in a more completely ossified sternum referred by me to this species in 

 my own possession, this last sternum measuring 15 inches, with a lunate 

 callosity two and a half inches across. The fact is, this fifth lunate callosity is 

 one of the generic characters in Trionyx in its perfectly adult state, though 

 sex may perhaps influence the size the lunate plate may assume. It cannot 

 therefore serve, as it has been made to do, in its nascent state, before the coali- 

 tion of the two osculant patches of the immature animal, as a generic 

 character of Landemania or any other genus. 



The second species alluded to above is represented in the Imperial 

 Museum by a stuffed female, half grown, the skull and sternum of which are 

 mounted for examination, and the superb skeleton of a male, fully adult, with 

 a sternum of 15 inches. This fine species seems to have been quite overlook- 

 ed or confounded with Tr. Jiurum, which, as I have shown above, is a 

 synonym of Tr. gangeticus, Cuv., and as it is requisite to bestow a name on 

 it, I propose terming it Tr. Bioclianani, n. sp., with the following synony- 

 my :— 



Tr.. Buchanani, n. sp. 

 Tr. Imrum Auctorum in part, 



I am not prepared to say wherein it differs externally from Tr, 

 gangeticus, Cuv., but it may be at once distinguished most easily by 

 its skull, which is more taper, and by the mandible possessing a me- 

 dian groove inside, quite different from the same bone in gangeti- 

 cus. It is closely "allied to Tr. stellatus, Geoff., but differs in having 

 a slightl}^ narrower head behind, and less pointed one in front, and by the 

 median mandibular groove, for in Tr. stellatus, in place of a groove, there is 



