OF THE SIVALIK HILLS. 



47 



of the grinding surface, and sharply truncated at the internal side at the 

 point. In taking the dimensions of the incisive teeth of the upper and 

 lower jaw from two specimens of adult animals we tind their proportions 

 as follows : — 



Inches. Metres. 



Diameter of incisor — upper jaw, 0.9 0.022 



Ditto ditto — lower ditto, 0.7 0.018 



If there is any fixed difference in the size of the teeth of each jaw, it 

 exists in the second incisor being a little less than the others. It may be 

 necessary to note here with regard to the number of molars in the lower 

 jaw, that amongst the great number of specimens before us of animals of 

 all ages, we see no mark or vestige of the first milk tooth, or that which, as 

 was mentioned before, falls and is not replaced ; and the space between the 

 adjacent molar and the canine is so contracted as hardly to admit of room 

 for another tooth ; but as this tooth exists in the upper jaw in every speci- 

 men in our possession, we may infer that its non-presence in the lower jaw 

 is accidental. In viewing the lower jaw in profile, we see that the anterior 

 angle below the canines is somewhat more abrupt, and more inclined to the 

 form represented as belonging to the European fossil species, the depth of 

 the inferior maxillary is more regular, and the form of the posterior branches 

 as before described, very different. The lower surface exhibits a width of 

 symphisis equal to that of the living animal, and the angle formed by the 

 branching off of the two sides is also similar. The width across the muzzle 

 from the exterior side of the canine alveolus to the other is comparatively 

 greater in the Sivalik fossil, and the extreme width of jaw, over the penul- 

 timate false molar, less. It will be seen that these differences of form cor- 

 respond with those of the skull ; the advanced position of the orbit and the 

 contraction of the sinus in which the infra-orbitary holes are situated, leading 

 to a modification in the whole form of the grinding surface. 



Having made the comparison with the Cape and existing Hippopo- 

 tamus, we will cursorily note the differences that strike us when comparing 



