THE THEORY OF ORGANIC EVOLUTION 183 



RECENT 



S/epAas Yq 



Steoodon fo 



PLEISTOCENE 



UPPER PLIOCENE). 



LOWER PLIOCENE 

 UPPER MIOCENE ) 



Mastodon ; /q 



Gomphofficrium 

 /o/io/rostr/s staoe 

 (^horfeninq 

 Chin) 



MIDDLE M/OCENE \ 



Mhrotion into I Gomphotherium 



North America 



I onousfidens, stooe 

 (lono chinj^^L 



G.mfh.ner. 'A WWER MIOCENE 



\IVll(l 



2 



UPPER OLIGOCENE 



WHEROUGOCENE 



Poloeotoastodon 'fy UPPER EOCENE < 

 Ml DOLE EOCENE 



ro/aeomasfodon 

 (lenothtnino chin) 



Moeritherium. 



(Short eft in) 



Moerifher/utn /i 



L OtYE/f EOCEA/E (ancestor unknown). 



Fig. 24. Evolution of the Elephant. (From Scott, "Land Mammals of West- 

 ern Hemisphere," published by the Macmillan Co. Reprinted by per- 

 mission.) 



