THE ORIGIN OF SPECIES 



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FIG. 193. 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', Moeritherium, Eocene. (After 

 Lull.) 



