72 THE UNIVERSITY SCIENCE BULLETIN. 
recognized until more complete specimens from the same locality 
and horizon are studied. That they belong to a short-necked 
plesiosaur is probable, and this may be Polycotylus or something 
allied to it; though if the horizon is the Pierre Cretaceous, as is 
probable, the generic identity would be more doubtful. The 
greater concavity of the dorsal centra also indicates a distinct 
genus. 
The cervical is flattened, nearly circular in outline, rather 
strongly concave; a single large vascular foramen below, but no 
ridge or fossae, but very slightly concave from margin to margin. 
The articular rim encroaches much on the exterior. 
The diapophyses stand out moderately; vertically elongate, 
connected by a narrow surface upward on the arch. The lower 
extremity of the articular surface, however, reaches pretty well 
down on the ventrum. 
Transverse diameter of the centrum 84 mm. 
Vertical diameter of the centrum 78 mm. 
Length 45-48 mm. 
The better of the two dorsals is deeply cupped, circular in out- 
line, with rather sharp rims, rather deeply concave on the sides 
and below, and circular in cross-section through the middle; 
vascular foramen situated high up on sides, above the middle. 
Length below 55 mm. 
Length above 51 mm. 
Transverse diameter 100 mm. 
Vertical diameter 92 mm. 
