y;^g ' EEPTILIA. 



Plain, near Tezpur, in Assam, close to the Brahmaputra ; but any way, the generic 

 term 'chaibassia selected by Theobald is an unfortunate one. 



Theobald referred tliis new sub-genus and Geoemyda to the family Testudi- 

 nidce, from which, however, their structure markedly separates them ; the structure 

 of Geoemyda, also that of Chaibassia, being essentially that of an Emyde. 



An inspection of the specimens from the Bishnath Plain in Assam, and a com- 

 parison of them with Blyth's types of O. tricarinata, conclusively prove that the two 

 are perfectly distinct species, but generically identical.^ 



In 1875, I described a tortoise from Arracan, which I referred to the Genus 

 Geoemyda and named G. depressa.' Mr. Theobald afterwards^ re-described the 

 same species under the name of Geoemyda arakana, from specimens in the Indian 

 Museum, Calcutta. 



I propose now to consider wherein these species of Geoemyda differ from one 

 another and from Emys, to which they are closely allied, and what the characters are 

 of Chaibassia. I regret that I have no example of G. spinosa to compare with these 

 forms. 



1 The animals from tbe Bishnath Plain are distinguished from Chaibassia tricarinata, Blyth, by the very much 

 larger and anteriorly broader first vertebral, the lateral margins of which are widely anteriorly divergent, the 

 posterior border straight and equalling one-half the breadth of the auterior border : the fourth and fifth vertebrals are not 

 so large as in C. tricarinata. In the latter, the gulars are triangular, while, in the Assam species, the external lateral 

 mar°-ins of the gulars are rounded. The anal plates of C. tricarinata are decidedly larger than in the Bishnath species, 

 in which the anal notch is smaller. The form of the shells of the two species is practically the same, viz„ elongately 

 oval, relatively highly arched, downwardly shelving at the sides, and very slightly broader posteriorly than anteriorly. 

 The female is somewhat contracted in the Assam form at the fifth, sixth and seventh marginals, with no reversion 

 of the marginals, which are very feebly denticulated. A nuchal plate in both species, and three raised ridges, the vertebral 

 the lono-est, involving all the vertebral plates ; the lateral ridge on the costals more feeble. The colour of the Assam shell 

 is black above, almost orange-yellow on the under surface ; the dorsal ridges, and the under surface and the margins 

 of the shell brio-ht yellow. The head black, with a broad reddish band from above each nostril, increasing in breadth 

 as it passes over the eye and over the tympanum, where it ceases ; a narrow similar band below the angle of the 

 mouth, along the inferior margin of the lower jaw. Skin of throat and neck pale blackish-brown, also the granulated 

 .skin of the limbs, hind quarters and tail. Fore-limb, below the elbow, covered externally with large black scales ; a few 

 lar^e black scales also behind the outer side of the wrist ; no large scales on outer sui-face of hind limb, except at the 

 outer margin of the foot, and on the hinder half of the sole; toes free ; hind foot rather club-shaped ; claws large, 

 shai-p and black. The colours of C. tricarinata are unknown. 



The head of the Assam form is more pointed than in C. tricarinata, and the facial portion longer. These 

 characters are pronounced in the skull, and the frontal region is much longer and nai-rower than the corresponding region 

 in C. tricarinata, and the palatine, but more especially the pterygoid 'region, is distinguished from the latter by its 

 great breadth. The following are the measurements of the two sexes, from which it would appear, as both are adults, 

 that the male is the smaller of the two : — 



Measurements of O. theobaldi. 



Total lengtli of carap.'ice 

 „ of pla«troa 



Axillary breadth 

 Inguinal „ 



Greatest breadth across back 

 Depth through shell 



I have much pleasure in connecting Mr. Theobald's name with this species. 

 - Ann. and Mag. Nat. Hist., 4th Ser., vol. xvi, p. 284, Oct., 1875 ; no proof of this paper having been sent me to 

 correct, it is full of blunders. 



' Desor. Cat. Rept., Brit. Ind., Calcutta, 1876, Errata et add., p. vii. 



