68 FIELD COLUMBIAN MUSEUM—GEOLOGY, VOL. II. 
angles to the dorso-ventral plane, for the radius; a second shorter 
and less thick one for the ulna joins this at a small angle; beyond 
- this, the thinned ulnar expansion is lost in the specimen, but doubt- 
less had two facets for the third and fourth bones of the epipodial 
row. On the ventral surface of the bone above, proximad to the 
middle, there is a large, stout rugosity for muscular attachment. The 
very strong muscle attached to it doubtless arose from the ventral 
surface of the coracoid. On the ulnar border of the bone, at its 
middle, there is a more pronounced, though smaller rugosity, for 
muscular attachment. The peculiar tooth-like projections on the 
outer posterior angle of the coracoid described in Dolichorhynchops 
osborni probably indicates the origin of the muscle inserted into 
this rugosity.” It may be called the ulnar mugosityaeegaee 
radial border, a little beyond its middle, there is a smaller and less 
strong rugosity which may be called the radial. The origin of the 
muscle inserted here probably was on the lower part of the scapula. 
The dorsal surface of the shaft is smooth, without muscular roughen- 
ing beyond the tuberosity. The distal portion of the bone is much 
expanded, thickest toward the radial side, and moderately thinned at 
the distal outer margin. 
Of the four muscular rugosities, which doubtless furnished 
attachment for nearly all of the muscles controlling the arm, those of 
the tuberosity are of course the largest, though the large roughening 
on the ventral side may have been for the insertion of more powerful 
muscles, which were of course much more effective from the greater 
mechanical advantage under which they acted. The movement here, 
though strong, could not have been through a reat range. » The 
smallest of all, and placed much further away from the fulcrum is 
the radial. The great convexity of the head indicates considerable 
freedom of rotation. The glenoid surface in the articulated skeleton 
of Dolichorhynchops looks nearly directly outward. The obliquity at 
which the head of the humerus is placed as regards the horizontal 
plane, indicates that the natural resting position of the flipper was at 
about forty-five degrees downward, but I doubt whether the extrem- 
ities of the paddles could have been raised much, if any, above a 
horizontal position. It is further certain that the flippers could not 
have been brought back against the side of the body. The posterior 
angle of the coracoid, projecting as it does beyond the plane of the 
glenoid surface, certainly prevented any great backward movement 
of the humerus. It seems also evident from this position of the cor- 
acoid, that the paddle was not so pedunculated as restorations usually 
have them, but that the humerus was largely or entirely hidden in 
