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ORIGIN OF LIFE IN AMERICA 
dence for the assumption that the general movement of the 
fauna has been from the Old World to the New. Finally, 
in the Pliocene beds of North America, we perceive clearly 
that an invasion of South American animals has taken 
place.* 
* Osborn, H. F., “ Cenozoic Mammal Horizons,” pp. 42—82. 
