746 



THE AMERICAN NATURALIST [Vol. XLI 



Phenacodus from the Wasatch. The trochlea is broatl with well 

 rounded articular surfaces for the radius and ulna. The anconeal 

 fossa is quite deep and broad, hut low. In this specimen (No. 

 1604) the radius and ulna are entirely co-ossifled. On the radius 

 the external articular facet for the humenis is considerably larger 

 than the internal, while on the ulna the internal articulation is very 

 extensive. On a direct front view the head of the radius lies in 

 front of the ulna, but immediately below the head on the external 

 side, the shaft of the ulna a^am appears. Tlie olecranon of the 



