NORTH AMERICAN PLESIOSAURS 



733 



time (fig. 14), it differs in the absence of the fourth epipodial, the 

 greater concavity of the ulnar border, the convexity of the distal 

 radial border, etc. 



Fig. 14. — P. laiipinnis. Left humerus, dorsal side, three-sevenths natural size. 



