THE MIOCENE PERIOD. 



321 



very large size, and are each composed of a number of trans- 

 verse plates of enamel united together by ivory ; and by the 



Fig. 247. A, Molar tooth of Elephas planifrons, one-third of the natural size, show- 

 ing the grinding surface from the Upper Miocene of India ; B, Profile view of the 

 last upper molar of Mastodon Sivalensis, one-third of the natural size from the Upper 

 Miocene of India. (After Falconer.) 



process of mastication, the teeth become worn down to a flat 

 surface, crossed by the enamel-ridges in varying patterns. 

 These patterns are different in the different species of Ele- 

 phants, though constant for each ; and they constitute one of 

 the most readily available means of separating the fossil 

 forms from one another! Of the seven Miocene Elephants 

 of India, as judged by the characters of the molar teeth, 

 two are allied to the existing Indian Elephant, one is related 

 to the living African Elephant, and the remaining four are in 

 some respects intermediate between the true Elephants and 

 the Mastodons. 



The Mastodons, lastly, though quite elephantine in their 



