ELEPHAS. 35 



teeth is nearly related to Tetrabelodon Ion giro stris, but the ridges 

 of the molars are comparatively higher. There is, however, as 

 yet no cement in the valleys (fig. 20), which are more or less 

 obstructed by small tubercles, and some of the cusps wear into a 

 trefoil pattern, as in Tetrabelodon angustidens and T. longirostris. 

 While, however, the anterior molars are almost identical with 

 those of T. longirostris , the posterior lower molar is very similar 



Fig. 21. 



Grinding-surface of a lower molar tooth of Mastodon sivalensis. 

 From the Lower Pliocene of the Siwalik Hills, India, f- nat. size. 



to that of M. laiidens, which in its turn approaches Elephas 

 (Stegodon) clifti (fig. 22) very closely. In M. latidens there are, 

 as a rule, five transverse ridges in the second upper molar and 

 six in the last. 



ELEPHAS. 



The next stage is represented by Elephas (Stegodon) clifti 

 (fig. 22) (Pier-cases 35, 36 ; Table-case 24, Stand K). With 

 this species we reach the true elephants, though the molars 

 have much lower crowns and fewer transverse ridges than in 

 the modern species of Elephas ; and, in fact, these earlier 

 forms are sometimes separated into another genus called 

 Stegodon. Since, however, no real line can be drawn between 

 them and the later types it is perhaps best to call all Elephas , but 

 distinguish these earlier forms by adding the name Stegodon in 

 brackets as above. In all this group the lower incisors have 

 entirely disappeared, the anterior elongation of the chin at 

 the same time being reduced to a mere peg-like process 

 (figs. 24 & 31), and a greater or less amount of cement (see 



D2 



