230 S. W. Williston — North American Plesiosaurs. 



The scapula, save the tip of the dorsal process, and the paddle 

 are in excellent preservation. The vertebrae have suffered 

 much from compression, as is usually the case with the soft- 

 boned plesiosaurs in the Kansas chalk. 



The scapula is figured in outline herewith (text-figure 4). 

 Its inner part is greatly expanded and produced to meet its 

 mate broadly in the middle line. At their symphysis the two 

 bones are extended backward in a narrow, elongated process, 

 which did not, however, unite with the coracoid, as was the 

 case with E. platyurus. In front, the two bones leave a 

 broad, angular interval for the clavicle or interclavicle. 

 Neither of these bones has ever been certainly defined in this 

 genus, though Cope figured the pectoral girdle of E. platyurus 



Figure 4. — Scapulae of Elasmosaurus marshii Williston. No. 2062, Yale 

 Museum. 



as meeting broadly in front, as though the clavicle were fused 

 with the scapulas. I believe that the missing bone is the 

 interclavicle, and that the clavicles will be found to be as in 

 Cryptoclidus. 



The structure of the paddle is clearly shown in Plate II, 

 figure 2, as arranged under the supervision of Professor 

 Marsh. I do not know under what conditions the bones were 

 collected, but doubtless they were sent in from the field 

 with the different parts dissociated. A careful study of the 

 mounted specimen, however, assures me of the essential cor- 

 rectness of the restoration. The peculiar form of the hume- 

 rus, quite unlike that of any other species of plesiosaur 

 known to me, will enable this species to be readily recognized, 

 though the characters of the scapulas and vertebras may possi- 

 bly be insufficient. The bone is short, as is seen, — an elasmo- 



