Apr. 1903. Norra AMERICAN PLESIOSAURS—WILLISTON. 4I 
lar cartilage. The ventral or clavicular (proscapular) extremity 
is broad and thin and deeply concave on its visceral surface. 
Its inner border is rounded for the most part and thin, except 

FiG.Y 6; 
Part of right scapula of Pleszosaurus mudgez Cragin, external (left,and internal (right) views. 
on the anterior part, where it is moderately thickened, as though for 
cartilage. The posterior and inner border is quite thin throughout 
and evenly concave, forming the outer anterior border of the scapulo- 
coracoidal foramen. The anterior border is sinuous and thinned, 
having a knife-like edge throughout its whole extent. The exterior 
border, between the glenoid and suprascapular extremities, is deeply 
concave, with the mar- | | 
gin thickened and 
convex. The ventral 
suriace of the bones 
forms two nearly flat 
planes, meeting in a 
straight, prominent 
ridge, which extends 
from the ventral side 
of the anterior border 
of the glenoid surface 
to the anterior angle 

of the ventral ramus. 
Thetwo surfaces meet 
Fig. 7. 
Ventral extremity of scapula of Plesiosaurus gulo Cope (type 
aia \veEDy O btuse specimen), one-half natural size. 
angle. The visceral 
surface is, for the most part, concave. On the ventral ramus this 
concavity is marked, receiving the clavicle on its anterior part. 
There is a Sutural roughening continued along the anterior border 
