138 THE DESEADO FORMATION OF PATAGONIA 
the fore arm. Most of the shaft is lacking but what is 
present indicates a very slender bone. 
The tibia is also a rather light bone of moderate length, 
and is strongly curved inward, the inner margin being 
Fig. 96. Upper end of 
radius, ulnar side—r1r/5 
natural size. 
Fig. 98. Astragulus, dorsal aspect—1 /2 
natural size, after Ameghino. 
: ana Fig. 09. A, Ungual phalanx, 
Fig. 07. Left tibia, posterior No. 3; B, Ungual phalanx, No. 
side—1/5 natural size. 5—r/2 natural size. 
especially concave. On the wide proximal end, the inner 
condyle is concave, the outer convex, the two being sep- 
arated by a prominent bifid spine. The shaft is slender, 
with a deep groove down the anterior face especially at the 
