438 



MEMOIRS OF THE -CARNEGIE MUSEUM. 



proximately correct, as it corresponds with those in Coenopus tridactylus Osborn 

 which was found, articulated, in the upper Oligocene of South Dakota.-* 



The first dorsal vertebra is characterized by the proportionally large and high 



Fig. 21. Fig. 22. 



Fig. 21. Diceratherium cooki Peterson. No. 2499, Coll. Carnegie Museum. Lateral and posterior views 



of seventh cervical. X h- 

 Fig. 22. Diceratherium cooki Peterson. No. 2499?, Coll. Carnegie Museum. Lateral and posterior 



views of first dorsal. X 5. 



neural spine and the depressed centrum; the prezygapophyses are also much ex- 

 panded laterally to receive the postzygapophyses of the last cervical. The articu- 

 lations for the ribs are located very low on the side of the centrum and the pedicel 

 is broad and heavy. 



With the exception of the skull, there is probably no other part of the skeleton 

 in this species which is subject to greater variation than the neural spines of the 

 dorsal vertebrae. In specimens undoubtedly referable to adult and old males 



28 Osborn, H. F., Bull. Amer. Mus. Nat. Hi.st., Vol. V, 1893, p. 85. 



