146 THE DESEADO FORMATION OF PATAGONIA 
is only large enough to actually cover about half of the head 
of the humerus, and fits so that, in a position of rest, the 
glenoid covered the outer part of the humeral head, and 
only articulated on the inner part of the humerus head 
when the limb was bent inward. The blade of the scapula 
is narrow, with the proximal end prolonged and ending 
in a thick rugose mass. The anterior and posterior mar- 
gins are rugose and thickened, the great thickness of the 
proximal end being due to the convergence of these thick- 
ened margins and the heavy spine. Lastly, this thick 
proximal end is peculiar in having on its posterior side a 
large rugose cavity, which was apparently to receive mus- 
cular attachments. 
For such a heavy animal, the humerus is extraordinarily 
long and slender. The sessile head is strongly compressed 
from side to side, very convex, and much larger than the 
glenoid fossa, its articular surface extending onto the base 
of the greater tuberosity. This tuberosity is heavy and 
thick, but does not project above the head. The powerful 
deltoid ridge extends from the tuberosity two-thirds of 
the way down the shaft. The shaft is unusually slender. 
Distally it expands laterally to make the two large epicon- 
dyles, of nearly equal size. The trochlea is relatively 
narrow, the internal surface being the narrower, and rising 
to a high margin; while the external portion is wider, 
rounded, and has a low margin. The supratrochlear 
fossa is moderately deep, the anconeal fossa somewhat 
deeper, but there is no connecting foramen. 
Gaudry* figures a radius and ulna, both relatively long 
bones, and closely apposed; so that there was no possibility 
of a rotary motion of the forearm. The proximal end 
of the radius is expanded, so that its articular surface 
is in contact with the full width of the humeral trochlea 
on the anterior side. Below, the bone contracts to a 
moderately slender shaft, and then expands distally into 
* Anal. Palaeontologie, t. 1, p. 5, 1906. 
