Apr. 1903. NorTH AMERICAN PLESIOSAURS—WILLISTON. 43 
membrane bone to attain on the visceral side of all three cartilage 
bones. The anterior border is gently thickened, somewhat sinuous 
in outline, and is free for a part of its extent. The other borders are 

Co rkee> 
Cen) 
CO 
Shee ; aes cet 
Fic. 8. 
Diagram of pectoral girdle of DoJlichorhynchops osbornz, from above; the outlines of con- 
cealed parts are indicated by dotted lines. /c., episternum (interclavicle); cé/., clavicle; sc., scap- 
ula; co., coracoid. 
thin, for the most part squamous, and nowhere free, save for a short 
distance at the anterior end of the coraco-scapular foramen, and the 
posterior part of the interclavicular foramen. The two bones meet 
