154 



FAUNA ANTIQUA SIVALENSIS. 



It differs from the existing Hog tribe and the Choeropo- 

 tamus, in the coronal not being an aggregation of tubercles or 

 rounded cylinders, but divided into four distinct portions, two 

 of which' are certainly conical. 



At first sight the fragment has a considerable resemblance 

 to certain species of Mastodon, in the form of the protuber- 

 ances and discs of detrition, such as the M. Andium ; but 

 the nearly square form of the shaft, the presence of only 

 two pairs of hillocks in a back grinder on a coronal along 

 with a spur, and another tooth of nearly the same form placed 

 before it, are proofs of molars in a series of several, and alone 

 sufficient to distinguish it from every species of that genus. 



The Anthracotherium has a coronal divided into four dis- 

 tinct pyramidal hillocks, with deep furrows between. In 

 these respects there is some resemblance in our fossil. But 

 the two differ materially. In the Anthracotherium the shaft 

 has a ridge or collar of enamel in relief around it ; and it is 

 strongly convex in its vertical section. The hillocks are a 

 little elevated, and their sides converge rapidly in a blunt 

 pyramid ; the surfaces by which these pyramids regard each 

 other throw off connecting sharp and sometimes bifurcating 

 edges, which make the coronal angular. Further, the upper 

 molars have four accessory tubercles, projecting from the 

 collar, alternating with the bases of the large processes. All 

 these characters are absent m our fossil, which has, in addi- 

 tion, positive points of distinction not present in the Anthra- 

 cotherium, such as the transverse crenulated ridges of enamel, 

 &c. These characters combined strongly mark the Anthra- 

 cotheriiim and the fossil as distinct genera. 



The only genus remaining for comparison is the Hippo- 

 potamus. At a casual examination the fossil seems sufficiently 

 distinct. But the essential points of structure in both are 

 so analogous as to require a strict comparison. 



The resemblance is this : — 



The last teeth of both have a square shaft surmounted by 

 a coronal, divided into four conical hillocks, brought together 

 by pairs, a transverse ridge or crest in front of the anterior 

 pair, and in the last molar an accessory solitary hiUock or spur. 



The points of difference are these : — 



In the Hippopotamus the pairs of conical processes are 

 brought together, and separated by a longitudinal irregular 

 cleft, of which the sides are nearly vertical. The processes 

 are marked on each side by a vertical narrow furrow, so that 

 in detrition the discs are trefoiled when the processes of each 



' This reservation is made, because, 

 althougli the four hillocks may well be 

 inferred to be distinct and conical, the 



detrition of the last tooth leaves the 

 character apparent but in two. 



