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THE AGE OF MAMMALS 



By permission of the U.S. Geological Survey. 



Fig. 35. — Heart of the ancient Eocene flood plain and lake region of Wyoming, showing 

 the areas of Eocene deposition which have resisted erosion. Lower Eocene : Wasatch (oblique 

 lines); Wind River (horizontal Unes) ; Green River (vertical lines). Middle Eocene : Bridger 

 and Washakie (horizontal lines). Upper Eocene : Uinta (horizontal lines). 



