1404 



CLASS MAMMALIA. 



the density of the different layers of which the tooth is composed. The 

 enamel-disks of both the species under consideration are, when partially 

 worn, generally expanded in the middle, and are often interrupted in 

 their course across the crown ; in the European species the enamel itself 

 being thrown into a series of fine plications, or crenulations. Both E. 

 meridionalis and E. ftlcmifrons attained gigantic dimensions, the height 



Fig. 1281. — Elefthas fila.7iifrons. Vertical and longitudinal section of the second upper true 

 molar ; from the Pliocene of the Siwalik Hills. One-third natural size. Letters as in fig. 1280. 

 (After Falconer and Cautley.) 



of some individuals of the former being estimated at upwards of fifteen 

 feet, while a fair average height of males of the existing Indian species is 

 not greater than nine feet. E. planifrons is remarkable as being the 

 only member of the Elephantine group in which premolars were devel- 

 oped. Somewhat more specialised, both in regard to the height and 

 number of the ridges of the cheek-teeth, and also in the elevation of the 

 vertex of the cranium, is E. hysudricus, of the Pliocene Siwaliks of India, 

 which may perhaps have been the ancestor of the existing species of 



Fig. 



>2. — Grinding surface of upper molar of Elephas planifrons, one-third natural size ; 

 from the Pliocene of India. (After Falconer and Cautley.) 



that country. In E. antiquus, of the Pleistocene of Europe, we have 

 a species with the ridges of the cheek-teeth somewhat more numerous 

 than in the last form, although less so than in E. primigenius ; their 



number being represented by the formula Mm. — (6-8) ' (o- 



M. fo-ia)- (12-13). (15-20 ) Th j (fi g ^ USU ally rela- 



(U-12). (I2-I3). (l6-2l) \ & 1/ / 



tively narrow, and there is very generally (especially in the lower jaw) 



