38 



Annals of the Carnegie Museum. 



ing), and it is separated from the occipital condyle by a shallow 

 notch, and is in contact with the posterior face of the tympanic bulla. 

 The occipital condyles have a small vertical diameter ; they are greatly 

 convex from above downward and widely separated laterally by the 

 emargination on the basioccipital. The foramen magnum is large. 

 The cone-shaped postglenoid process is rather small when compared 



Fig. 7. 1, side view of skull of Merychyus harrisonensis. 2, top view of skull, 

 nat. size. Type. No. 1341. 



with that of Merycoidodon culbertsoni and Phenacoccelus typus. The 

 tympanic bulla occupies a large area of the base of the cranium and 

 has a peculiarly depressed and flask-like form. There is a conical 

 swelling on the postero-external angle of the bulla, and a deep emar- 

 gination or pit near this eminence for the tympanohyal which constricts 

 the otherwise broad tube of the external ear. The postorbital process 

 is of moderately large size and the orbit was apparently closed 

 posteriorly. 



The alveolar border of the maxillary is lower even than in Mery- 

 coidodon culbertsoni. The infraorbital foramen is double and is located 



