Apr.1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 49 
the cartilage continued to the rounded outer anterior angle, where 
the bone isa little more thickened. The acetabular surface is much 
the larger of the articulating facets. It meets the smaller and rough- 
ened facet for the ischium in a very obtuse angle. The bone is more 
thickened on the outer and posterior parts, that is, near the non- 
cartilaginous border, than elsewhere. (See Pl. XVI.) 
le: 
pu 
LS 

FIG: 12. 
Diagram of pelvic girdle of Dolichorhynchofs osborni, visceral surface. Pw., pubis; zs., ischium; 
a/.. ilium., 
The ¢schivm is more elongate and proportionally larger than is 
usual among plesiosaurs, though of the usual hatchet shape. It has 
three non-sutural articular surfaces—the larger middle one, looking 
directly outward in the articulated ischium; a smaller posterior one, 
