FOSSIL GENERA of the SUB-HIMALAYAS. 



57 



them the smallest, and the exterior ones hold a mean between the 

 two. No whole jaw of this description is in the collection, and the frag- 

 ments are such as not to warrant any deductions from the distinctions 

 here noticed. Fig. 4, PI. IV, presents a marked difference in the shape 

 of the incisors, which are more elliptical than in the preceding varieties. 

 The exterior incisors have a section not observable in any other speci- 

 men ; and are, relatively to the four centre incisors, set lower than the 

 analogous incisors of other varieties— may not this be considered a distinct 

 species ? 



Fig. 3, PI. V, is a fragment from the lower jaw of a small Hippopo- 

 tamus, it contains the two posterior molars, the advanced one differs in shape 

 and proportionate dimensions from the analogous molars of the larger 

 species ; the fore part of the tooth is much narrower than the after part ; 

 the length of the tooth measured along the jaw is equal to that of the same 

 tooth in the larger species, the jaw is more curved and fines off more 

 rapidly towards the front than in the larger animals : it is so narrow in front 

 of the advanced tooth as to suggest the possibility of their having been 

 fewer molars than seven. 



Hippopotamus — Upper Jaws. 



Fig. 1, a, b, PI. VI, is from the head of an old animal, the teeth being- 

 very much worn : the specimen is so much cracked, that the sandstone 

 could not be cleared from the temporal fossa. On comparison with the 

 species described by Cuvier many differences may be observed. I shall 

 however confine myself to noticing a few distinctions which exist 

 among the specimens before me, without alluding to those which will 

 immediately strike the eye on comparing Cuvier's plates and the accom- 

 panying sketches. 



Fig. 1, PI. V, is taken from a specimen, the head of an adult animal ; 



it varies from the former in the shape and prominence of the orbits, in the 



p 



