1589.] R. Lydekker — On the Turtoises described as Chaibassia. 329 



ThrcG years later Dr. J. Ander.son* gave a further description of 

 Chaibasda, iu wliioli he described it as allied to Geoemyda, but with a 

 bony temporal, or zygomatic arch, the feet not webbed, and the hypo- 

 plastrals usually attached to the carapace only by ligament.f The Assa- 

 mese form was hero described under the name of O. theohaldi, and was 

 stated to differ from the type species by the contour of the first vertebral 

 shield, the longer facial portion of the head, and certain slight details of 

 coloration. 



In his ' Catalogue of Cheloniaus,'J Mr. Boulenger introduced the 

 genus Chaibassia, on the authority of Anderson, after Qeoemyda, stating 

 that its characters required further investigation, and omitting it from 

 the number of well-authenticated genera. The characters of the two 

 so-called species were likewise given, as culled from the description of 

 Messrs. Theobald and Anderson. 



On comparing the shell of the male specimen from the Naga Hills 

 (of which a lateral view is given in Fig. 1, A ) with that of the typical 

 female shell from Chota Nagpur (Fig. 1, B. 0.), it is at once apparent that 

 the slight difference in the contour of the first vertebral shield, and also 

 the slight variation in colour, are but individual peculiarities ; and that 

 still more marked variations occur in the large series of specimens of 

 Nicoria trijuga preserved in the British Museum. Thei'e has, indeed, been 

 no opportunity of comparing the heads of the Assam and Bengal forms, 

 but I cannot regard the alleged longer muzzle of the former as auythiug 

 more than an individual variation. There is, indeed, one very striking 

 difference between the two shells, viz., that, whereas in the Bengal 

 specimen the hypoplastrals join the carapace merely by a ligamentous 

 attachment, in the Assam specimen there is a perfect sutural union 

 between the two. In the face, however, of the resemblance of the two 

 speeimons in all other respects, it appears, both to Mr. Boulenger and 

 myself, that we have again to do with a variation which cannot 

 be regarded as of more than individual importance, although, as 

 will be shown below, it is one which appears to be of comparatively 

 common occurrence. The result, then, of this comparison is to show 

 that Chaibassia theubaldi is not specifically separable from the tortoise 

 described as 0. tricarinata. 



With regard to the generic position of this form it will bo evident 

 from the preceding observations that the occasional ligamentous union 

 cf the hypoplastrals with the carapace can be of no importance from this 



* Zoological Eesalfca of Yanan Expeditions, pp. 718-720 (1879). 

 t Some confusion in this description is pointed out by Boulenger ' Catalogue,' p. 

 139, note 



X P. 139. 



