1400 



CLASS MAMMALIA. 



the ridges of the cheek-teeth (fig. 1276) are nearly straight, and the in- 

 tervening valleys only partially blocked by tubercles. The latter wood- 

 cut shows the progressive increase in the number of ridges of the milk- 

 molars of the present group ; the first and second true molars, which 



Fig. 1275. — Left lateral view of the imperfect skull of Mastodon longirostris ; from the 

 Bone-sand of Hessen-Darmstadt. Much reduced. (After Kaup.) 



would follow the fourth milk-molar (the right-hand tooth in the figure), 

 each have the same number of ridges as the latter. M. Cautleyi, of the 

 Pliocene of Western India, is a form connecting the last species with M. 

 latidens. The latter is very widely distributed, ranging in the Pliocene 



Fig. 1276.— The three left upper milk-molars of Mastodon longirostris ; from the 

 Bone-sand of Hessen-Darmstadt. (After Kaup.) 



from India and Burma to Borneo ; the symphysis of the mandible is 

 short ; the molars (fig. 1277) are very wide, with their ridges and valleys 

 straight and uninterrupted ; and these teeth pass so completely into the 

 type of those of the least specialised species of Elephas as to indicate 



