PALEONTOLOGY: H. F. OSBORN 



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traced back to the Upper Eocene in both countries; it is thus of Holarctic 

 distribution, and while very rare, it must have been perfectly adapted to its 

 environment, because it survived the majority of perissodactyls and occurs in 

 the Pliocene of Europe and England and will not improbably be found in 

 the North American Pliocene. 



The habits and habitat of the animal have alw^ays presented a very difficult 

 problem. The skeleton presents the most noteworthy exception to Cuvier's 

 law of correlation. All the foot bones which were discovered since Cuvier's 



FIG. 1 



Mounted skeleton of Moropus cookei in The American Museum of Natural History. One 

 of the seventeen. Drawing one twenty-sixth natural size. 



time consisted of large deeply-cleft terminal phalanges and were grouped 

 with the edentates, especially the plantigrade sloths. All the teeth which 

 were discovered, on the other hand, were grouped with the perissodactyl 

 ungulates. It was not until H. Filhol discovered the nearly complete skeleton 

 of Macrotherium that he was enabled to prove that the chalicotheres were of 

 composite adaptive structure, with the teeth of perissodactyls and the claws 

 of edentates. Macroiherium is very similar to the American Moropus. 



Great light was thrown upon the structure of Moropus through the explora- 

 tions of the Carnegie Museum by Holland and Peterson, described in 1914, 

 from materials collected in the famous Agate Spring Quarry, Sioux County, 



