1889.] R. Lydekkor — On the Tortoises described as Chaibassia. 331 



jDoiut of view. Furtlier, on comijarison with the representatives of the 

 Oriental and Neotrojjical genus Nicoria (Melanochelijs) , it appears that 

 the chelonian under consideration agrees in all respects with the defini- 

 tion of that genus given by Mr. Boulenger,* which is as follows : 



" Neural plates mostly hexagonal, short-sided behind, or alter- 

 nately tetragonal or octagonal. Plastron extensively united to the cara- 

 pace by suture, with short axillary and inguinal buttresses, just reaching 

 the first and fifth costal plates respectively ; entoplastrou intersected by 

 the humero-pootoral sature. Skull with a bony temporal arch ; alveolar 

 surface without a median ridge ; choanas between the eyes. Up])er 

 surface of head covered with undivided skin. Digits with a short wob, 

 or without. Tail short, not longer in the young than in the adult." 



In the Sirguja specimen, with the exception of the one between the 

 hyo- and hypoplastrals, the whole of the sutures between the bones of 

 the shell are completely obliterated ; but, on raising the second vertebral 

 shield of the Assam specimen, it was seen that the underlying neural bones 

 have the characteristic features of Nicoria ; while, on the plastron, the 

 intersection of the entoplastral bone by the sulcus dividing the humeral 

 and 2^ectoral shields is distinctly visible. The short axillary and ingui- 

 nal buttresses are also displayed in the female shell ; while the skull of 

 the male exhibits the undivided skin on tlie upper surface, the presence 

 of a temporal arcade, the absence of an oral ridge, and the position of 

 the posterior nares (choauEe) on the transverse line of the orbits. The 

 digits have an almost imperceptible web, and in this respect approxi- 

 mate to the South American N. annulata, in which the ^veb is totally 

 wanting. The shortness of the tail is well shown in the figure. 



It appears, therefore, to be quite clear that the genus Chaibassia 

 should bo included in Nicoria, and that the one sfjecies of the former 

 should be known as Nicoria tricarinata. 



Mr. Boulengerf divides the six speoies of Nicoria recognised by him 

 into two groups, the first of which is characterized by its tricai'inate 

 carapace, and includes the Oriental N. spengleri and N. trijuga, while the 

 second has a unicarinate carapace, and is exclusively American. In 

 N. trijuga and apparently in JV". spengleri the digits are distinctly webbed, 

 and the posterior por*^ion of the carapace slopes gradually from tho 

 vertex to the margin. The almost total absence of webbing in tiie 

 present siJcoies, and the abrupt descent of the posterior jjortiou of the 

 carapace, indicate terrestrial habits ; and it thus appears that N. tricari- 

 nata is a representative of the Oriental tricarinate group of the genus 

 occupying an analogous position to that held in the Neotropical wiicari- 



* Catalogue, pp. 118, 119. 



t loa. cit. 



