HIPPOPOTAMUS. 131 



curved downwards, and those in the lower projecting forwards 

 (PI. XII. fig. 3) ; the diameter of these teeth, which are cylinders 

 ■with truncated, ends, is less in the npper than in the lower jaw, 

 and the central teeth maybe considered as being in some degree 

 larger than those on the right and left. When we advert to 

 the uses to which the incisive teeth of this unwieldy animal 

 are applied, the means of tearing up the food, and the sieve 

 to cleanse that food afterwards,' we see in this form of tooth 

 and this arrangement of the muzzle, an adaptation to the 

 wants as perfect as, although for defence less powerful than, 

 in the existing species. With the six incisors our fossil 

 animal has the canine teeth of the upper jaw with a reniforra 

 outline in transverse section, whilst that of the lower jaw is 

 pyriform, or pear-shaped. The molars resemble those of the 

 existing species, and are numerically the same; the first milk 

 or deciduous tooth which, as in the horse, falls and is not 

 again replaced, is here also conspicuous. 



In j)roceeding to a comparison between the fossil head and 

 that of the Cape Hippopotamus, we are at once struck with 

 the position of the orbit of the Sewalik fossil. Viewing it in 

 profile, the orbit is considerably more advanced, and the 

 general contour of the head thereby modified (PI. XI. fig 3); — 

 taking a measurement from the posterior extremity of the oc- 

 cipital condyle to the anterior ridge of the orbit, and from that 

 point to the front of the muzzle, we have in the existing animal 

 a proportion of 3 to 5, and in the fossil 9 to 13^, giving to 

 the orbit of the latter a more central position on the face ; this 

 peculiarity leads to the muzzle and the zygomatic arch beinr 

 separated by a hollow much more abrupt and much shorten 

 on its antero-posterior line than in the Cape Hippopotamus 

 (figs. 1 & 2). The anterior termination of the zygomatic arch 

 on the malar angle is more acute, and the general form of this 

 arch more prominent. The temporal fossae are longer, and 

 the temporal apophysis in its descent to join the malar bone 

 is slightly inclined forwards, placing the posterior angle of 

 the zygomatic arch in a more advanced position, and more 

 in front of the occipital surface, than in the existing animal. 

 The occipital crest is also more elevated, and the general 

 appearance differs, owing to this position of the orbit; 

 which, as will be naturally concluded, leads to a different 

 proportion in the bones of the head, those of the cranium 

 being lengthened, whilst those of the face are shortened in 

 proportion respectively. In the suture separating the 

 temporal apophysis from the jugal, we see the same direc- 

 tion and inclination as in the existing animal. 



' Vide Lancet : Professor Grant's Lectures. 

 K 2 



