CENOZOIC ERA: AGE OF MAMMALS 



637 



middle: eocene 



Fig. 561. — Map of the world in the Middle Eocene, showing the isolation of the 

 continents and the conditions favorable for the development of provincial faunas. 

 (After W. D. Matthew.) 



OLIGOCENE 



Fig. 562. — The separation of Africa and South America from their neighboring 

 continents caused the animals of the former to develop independently, while the union 

 of Asia to North America permitted intermigration between these continents. (Aftei 

 W. D. Matthew.) 



