EXPLANATION OF PLATE. 



Figure one-sixth natural size. 



Cymbospondylus petrinus Leidy (?). 



Pectoral arch, external side; anterior limb, inferior side. E, radius; U, ulna. 



The constriction of the ulna is immediately above the letter U. 

 The broad, cartilage covered marginal faces of the ulna are 

 discontinued suddenly at the upper and lower ends of the pos- 

 terior emargination. 



