1 8 CONTENTS 



CHAPTER XXI 

 CENOZOIC ERA: THE AGE OF MAMMALS. TERTIARY PERIOD 



VAGE 



Comparison of the Life at the Close of the Mesozoic and the Beginning of 



the Cenozoic 57 2 



Subdivisions of the Cenozoic Era. 



Physical Geography of the Tertiary 574 



Eocene ' .... 574 



Atlantic and Gulf Coasts. Pacific Coast. Western Interior. Eocene of 

 Other Continents. 



Oligocene 577 



Atlantic and Gulf Coasts. Western Interior. Pacific Coast. Oligocene of 

 Other Continents. 



Miocene 579 



Atlantic and Gulf Coasts. Economic Products of the Miocene. Western 

 Interior. Pacific Coast. Mountain Building. Basis for Separation 

 into Periods. Igneous Activity. Miocene of Other Continents. 



Pliocene 585 



Atlantic and Gulf Coasts. Western Interior. Pacific Coast. Pliocene 

 Elevation. High Plains and Bad Lands. Pliocene of Other 

 Continents. 



Life of the Tertiary 590 



Rise of Mammals. Archaic Mammals of Ancient Ancestry. Amblypoda. 

 Ancestors of the Carnivores. Marine Mammals. Zeuglodon. An- 

 cestors of Existing Whales. Ancestors of the Hoofed Mammals 

 (Ungulates). Divergence of the Even and Odd-toed Hoofed Mammals 

 (Ungulates). 



Factors in the Evolution of Mammals 600 



Mammalian Teeth. Feet. Limits to Evolution. 



Odd-toed Mammals (Perissidactyls) 603 



Titanotheres. Rhinoceroses. Tapirs. Horses. Summary of the Evolution 

 of the Horse. Probable Cause of the Evolution of the Horse. Cause 

 of the Extinction of the Horse in North America. Elephants. Sum- 

 mary of the Evolution of the Elephant. 



Even-toed Mammals (Artiodactyls) 615 



Camels. Deer. Cattle, Sheep, and Goats. Swine and Related Animals. 

 A Climbing Ungulate. 



Insectivores 620 



Rodents (Gnawing Animals) 620 



Edentates 621 



True Carnivores 622 



Primates (Monkeys, Apes, Lemurs) 622 



Birds 623 



Reptiles and Amphibians 624 



625 



