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 PHocene of Europe and England and will not improbably be found in 
the North American Pliocene. 
The habits and habitat of the animal have always 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. Macrotherium 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, 
