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w 

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0) 



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O <u 

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Recent 



Pleistocene'' 



Pliocene 



Blanco 



Ogalalla 



Pliohippus 



Miocene 



Arickaree 





John D9m««9m, 

 Oligocene white Rive. ' 



Uinta 



Eocene Bridget 



Merychippus 



Mesohippus 

 Orohippus 



ii il 



''^S^ 



^, — «..- > 



Wasatch — - ir u ■ 





#1 



Paleocene Ipuerco and To5i)^ 



Cretaceous ?»f;3 

 Jurassic 

 Triassic 



Fore* Hind- Premolar 

 foot foot teeii 



;^ 



-^ 



After Mattlii'us, American Museum of Natural History 



ANCESTORS OF THE HORSE IN AMERICA 



The oldest of the fossils do not resemble the corresponding parts of the modern horse 

 very strikingly, but with each succeeding age the skulls, the bones of the feet> and 

 the teeth resemble those of the horse more and more closely 



thousands of various kinds of bones. They recognized some of these bones as 

 coming from famiUar animals, such as were currently being swallowed up in 

 the tar. From lower depths, however, there came bones which nobody could 

 recognize. At last, when it was no longer profitable to work the bed, scientists 

 got their chance. They brought up probably several million bones, which 

 they began to clean and put together. 



A remarkable thing about these unmistakable bones was that they repre- 

 sented forms of life which no human being had ever seen on this continent. 

 There were gigantic members of the cat family, lions and saber- toothed tigers, 

 large bears, mastodons, elephants, camels, extinct types of horses, wolves, and 

 bisons. Any doubt that fossils were really the remains of animals and plants 

 that at one time lived upon the earth is definitely cleared up by the bones 

 from Rancho La Brea. If the facts are unmistakable, however, there is still 

 room for argument about their interpretation. 



453 



