CENOZOIC ERA 



215 



FIG. 10.16. Skull of Masfodon. (After Lull, Organic Evolufion, The Macmillan Company, 

 1945.) 



development of air cells but they were arranged in such a manner that 

 the "highbrow" appearance of true elephants did not result. The molar 

 teeth were low-crowned, long-rooted, 

 and had on the surface three or four 

 transverse crests, without cement in 

 the intervening valleys (Fig. 10.17). 

 We note that this tooth structure con- 

 trasts sharply with that of elephants 

 (Fig. 10.10). But two fully formed 

 molars occupied each jaw at any one 

 time. Judging by stomach contents 

 found associated with some American 

 mastodon specimens, the latter were 

 forest dwellers, including in their diet 

 twigs of such coniferous trees as hem- 

 lock and spruce. 



Mammoths and Elephants 



FIG. 10.17. Molar tooth of Mastodon. 

 (From Scott, A History of Land Mam- 

 mals in the Western Hemisphere, p. 

 417. Copyright 1937 by American 

 Philosophical Society. Used by permis- 

 sion of The Macmillan Company, pub- 

 lishers.) 



True elephants, including the Asi- 

 atic and African species and the ex- 

 tinct mammoths, are believed to have 

 arisen from the Asiatic form, Stegodon 

 (Fig. 10.11). In structure of molar 



teeth Stegodon presented a condition somewhat transitional between the 

 structures of mastodon and of elephant teeth. The transverse crests were 

 more numerous than they were on mastodon teeth, yet the amount of ce- 

 ment between the crests was not so great as it was in elephant teeth. Ele- 



