238 



[Nov. 15, 



the joint length in the Sewalik fossil being 1*8 inch, whereas in 

 the smaller jaw oi A. commune it is 2*3 inches. In the latter, as is 

 the case in the ruminants, the anterior premolars are narrow and 

 elongated ; in the Sewalik fossil they are short and wide. This 

 general condensation of the premolars adds to the probability of the 

 existence of a vacant diasteme. All the premolars exhibit, in a well- 

 developed form, the characteristic cusp. The posterior two have 

 their outer surface flat or slightly convex ; and they contract inwards 

 towards the cusp in a subcuneiform shape, the cusp and inner side 

 being bounded by a low basal ridge. 



The antepenultimate premolar of the Sewalik fossil is somewhat 

 different from the two others, being much smaller, and contracting 

 upwards into a trenchant edge. The cusp is connected by a trans- 

 verse ridge with the main ridge of the crown, and the basal ridge 

 is reduced to a small mammilla in front of the cusp. 



PL II. fig. 2. represents the outside of the right upper jaw, 

 comprising the four back molars, and is an exact counterpart, so 

 far as it goes, of the left upper jaw. 



There is little else shown by this specimen than what regards the 

 teeth. The muzzle appears to have fined off rather abruptly in front 

 of the malar protuberances, and the orbit to have been advanced 

 more forward on the face, and to have been more depressed below 

 the brow than in A. commune*. The upper orifice of the suborbi- 

 tary canal is seen opening behind the anterior angle of the orbit, 

 the floor of which appears to have extended behind the post-orbitary 

 processes. 



The dimensions, as compared with those of A. commune, and Cha- 

 licotherium Goldfussi, are as follow : — 



Length of the series of 6 molai-s 



Ditto 3 true molai's 



Ditto 3 premolars 



Length of the last true molar 



Width of ditto 



Length of the penultimate true molar 



Width of ditto 



Length of the antepenultimate true molar. 



Width of ditto 



Length of the last premolar 



Width of ditto 



Length of the penultimate premolar 



Width of ditto 



Length of the antepenultimate premolar. . 



Width of ditto 



Height of the last molar 



A. Sivalense. A, commune. Ch. Goldfussi 



Inches. 

 5-5 

 3-7 

 1-8 

 1-3 

 1-5 

 1-4 

 1-55 

 1-1 

 11 

 0-75 

 0-88 

 0-70 

 0-80 

 0-55 

 0-55 

 11 



Inches. 

 5-5 

 3-2 

 2-3 

 1-2 

 1-2 

 1-2 

 11 

 1- 

 l-l 

 0-65 

 0-75 

 0-90 

 0-62 

 0-75 

 0-50 

 0-65 



Inches. 



1-8 

 1-94 



0-87 



These measurements show the Sewalik species to have been larger 

 than A. commune, and smaller than Ch. Goldfussi. One of the most 



* See Ossemens Fossiles, torn. 3. tab. 57. fig. 1. 



