Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 51 
by the aid of a nearly complete paddle of another species, described 
further on. This paddle was less compressed and distorted, and I 
have therefore reserved it for a more full description of the parts and 
discussion of the functions. 
The humerus of Dolichorhynchops has the head only moderately 
convex, with its margins rather sharply limited, its greater convexity, 
as usual, on the radial side; its general surface looks mesad and 
_ventrad at an angle of about forty-five degrees. Its cartilaginous 
surface is continuous with that of the tuberosity, which has a large, 
flat surface, directed dorsad and mesad at an angle of about forty-five 
degrees. Ihe grooves separating the surface from the head are 
broad and shallow, that of the ulnar side the broader. The anterior 
border of the bone is concave on the proximal part, gently convex at 
the middle and shallowly concave on the distal part. The posterior 
border is nearly straight on the shaft, deeply concave distally. The 
distal anterior angle is rounded in both specimens. On the distal 
border two facets are apparent, for the radius and ulna; the rest of 
this border presents no clear indications of. articulations. The 
pectoral rugosity is strongly roughened, and produced into a broad, 
low tubercle; the roughening, moreover, is continued obliquely nearly 
to the other rugosities on the sides. It is situated nearer the head 
than in Polycotv/us. The ulnar rugosity forms a deep pit above the 
middle of the bone, while the radial rugosity is opposite it and much 
nearer the head of the bone than in Polvcotylus. 
Three bones were certainly located in the fore-arm, and a fourth 
one seems to be represented by a pair of small nodules. The free, 
emarginate border between the radius and ulna is less apparent than 
itis in Polycoty/us. The relations of all the smaller bones seem to 
be quite as they are in Polycoty/us, and the reader is referred to the 
figures of the two paddles for comparison, in connection with the 
description of that of Polycotylus. 
Hind Limps.—The femur shows the usual plesiosaurian differences 
from the humerus, in its greater slenderness, shghtly greater length, 
more slender shaft and less dilated distal extremity. The anterior 
border, as seen in the figure, is nearly uniformly concave, terminating 
in a more pronounced angle than in the humerus. The posterior 
border is, also, concave throughout to the greatest expansion, which 
occurs more proximally than in the humerus, and in a rather better 
marked angle. The rugosities of the under side and margins are as 
in the humerus, though scarcely as well marked. Whether the bones 
of the leg and ankle have been cotrectly located, rather than in the 
