DESCENT WITH CHANGE 



371 



f r 



Fig. 238. — Evolution of the head and molar teeth of Elephants. A, A', 

 Elephas, Pleistocene; B, Stegodon, Pliocene; C, C, Mastodon, Pleistocene; 

 D, D', Trilophodon, Miocene; E, E', Palaeomastodon, Oligocene; F, F', Moeri- 

 therium, Eocene. (From Lull.) 



