OF THE SIVALIK HILLS. 41 



that of the loM^er 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 proceeding 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 Sivalik fossil. Viewing it in profile, the orbit is considerably more 

 advanced and the general contour of the head thereby modified ; — taking 

 a measurement from the posterior extremity of the occipital 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 centrical position on the 

 face ; this peculiarity leads to the muzzle and the zygomatic arch being 

 separated by a hollow much more abrupt and much shorter on its antero- 

 posterior line than in the Cape Hippopotamus. 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 directioii and inclina- 

 tion as in the existing animal. 



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