38 



Annals of the Carnegie Museum. 



In Diploceras oshorni the antero-posterior diameter of the atlas is 

 rather small, while transversely it is propoitionally greater than in 

 the Oligocene forms. This is due in a great measure to the longer 



Fig. 3. Diploceras osborni Peterson. (Type. No. 2859.) X 3. Posterior 

 view of atlas. 



transveise process of the Uinta form. The cotyle for the occipital 

 condyle is also deeper and the groove for the odontoid process of the 

 axis extends further forward on the inferior arch due probably to the 

 propoitionally longer odontoid in Diploceras oshorni. 



Fig. 4. Diploceras osborni Peterson. (Type. No. 2859.) X \. Posterior 

 and lateral views of axis. 



Axis. — The axis of the type is represented by a portion of the 

 centrum, the complete neural arches, and the spinous piocess. The 

 arch is somewhat depressed by crushing, but it is evidently of rather 

 large size. The vertebra as a whole possibly has a smaller antero- 

 posterior diameter tiian is the case in most of the Titanotheres of the 



