HYRACOIDEA AND PROBOSCIDEA. 



381 



as to render it impossible to limit them with absolute pre- 

 cision. The three sections in question are the following : — 

 1. Eiielephas. — Dental lamellse narrow and compressed, 

 the number of the ridges successively increasing in the 

 three true molars from before backwards. The type of this 

 section is the living Elephas Indicus (fig. 662, a), the "ridge- 

 formula" of which is 12 + 16 + 24 — that is to say, there 

 is a progressive increase in the number of the transverse 

 enamel-ridges of the true molars, the first having twelve 

 of these ridges, the second sixteen, and the third and last 

 twenty -four. Besides the living Asiatic Elephant, the 

 section Uuelephas includes the Post - Pliocene Mammoth 

 (U. primigenms, fig. 663), the Eleplias antiquus of the 



Fig. 663.— Molar of the Mammoth (Eleplias prwiigenius), upper jaw, right side, half 

 natural size. Post-Plioceue. a, Grinding sm-faee ; 6, Side view. 



European Pliocene and Post-Phocene (fig. 666), and the 

 Elephas hystidricus of the Upper Miocene of the Siwalik 

 Hills, besides other forms of less importance. 



2. Loxodon. — Dental lamellae lozenge-shaped or diamond- 

 shaped, not greatly different in number in the three true 

 molars. The type of this group is the living Elephas 

 Africanus (fig. 662, b), in which the "ridge-formula" is 

 7 + 8 + 10. Among the other forms belonging to this 

 section may be mentioned EUplias planifrons (fig. 664) of 

 the Upper Miocene (Siwalik formation) of India, E. meri- 



