10 



ELEPHANTS, RECENT AND EXTINCT. 



grinding surface of the tooth of such an elephant con- 

 sequently consists of a solid mass, made up of alternating 

 vertical transverse layers of various substances, arranged 



Fig. 6. — Molar Teetli of Indian (a) and African {b) Elepliant. 

 In a the anterior half is worn, and the remainder nnworn. 

 Much reduced. (After Owen.) 



in the order of cement, enamel, ivory, enamel, cement ; 

 and since each of these constituents diiiers in hardness, it 

 •will be obvious that tlie millstone-like apparatus is now of 

 a far more efficient type than it was in the mastodon. 

 Moreover, since the crowns of the molars of the true 

 elei^hants are very much taller than are those of the 

 mastodons, it is evident that they will require a longer 

 period of time before they become worn away, and that 

 they will therefore allow a longer life to their owner. 

 Even, however, among true elejihants there is a con- 

 siderable amount of difference in regard to the number 

 and narrowness of the component plates of their molar 

 teeth, and it will be seen from Fig. 6 that in this respect 

 the African elephant departs far less widely from the 

 mastodon than does its Indian cousin. Since the food of 



