402 



MEMOIRS OF THE CARNEGIE MUSEUM. 



copei (Osborn) from the lower Oligocene (Metamydon beds) may be looked upon 

 as at least in the line of this family. ' 



While the general trend of the characters of Coenopus tridactylus and Coenopus 

 dakotensis sp. nov. is obviously in the direction of Dicer atherium, it is in the John 

 Day that we first recognize the genus as occurring in America. The South 

 Dakotan and especially the Nebraskan series of Diceratheres are a later group 

 belonging to the lower Miocene, closely following the species of the John Day, while 

 the so-called R. oregonensis Marsh is an inadequate type, which furnishes infor- 

 mation altogether too meager to be assigned to Diceratherium as is done by Pro- 



2 Osborn, H. F., Mem. Amer. Mus., Vol. 1, 1898, p. 164. 



