OMNIVORA. 



343 



which has only two lower incisors, and which is, therefore, 



often placed in a separate genus under the name of Chceropsis. 



Lastly, we have a series of forms from 



the Upper Miocene of India, which have 



been raised to the rank of a suh-genus 



(ITexaprotodon) , upon the ground that the 



lower jaw has six incisors (fig. 640, c). 



So far as at present known, the genus 

 Hippopotamus is an exclusively Old 

 World type, no member of the group 

 having hitherto been detected in the 

 Tertiary of the American continent. 

 The earliest forms of the genus belong 

 to the section Kexaprotodon, and are 

 found in the Upper Miocene deposits of the Siwalik Hills 

 in India. In the later Tertiaries of Europe several species 



Fig. 639.— Molar tooth of 

 Hi2}popotaimts, two - thirds 

 of the natural size. Post- 

 Pliocene. 



Fig. 640. — a, Skull of Hippopotamus Sivalensis, viewed from below, one-eighth of the natural 

 size ; b. Molar tooth of the same, showing the surface of the crown, one-half of the natural 

 size ; c, Front of the lower jaw of the same, showing the six incisors and the tusk-like canines, 

 one-eighth of the natural size. Upper Miocene, Siwalik Hills. (After Falconer and Cautley.) 



of Hippopotamus are known, of which the most important is 

 the Hippopotamus major of the Pliocene and Post-Pliocene. 



