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 — 1/5 

 natural size. 



Fig. 98. Astragulus, dorsal aspect — 1/2 

 natural size, after Ameghino. 



Fig. 97. Left tibia, posterior 

 side — 1/5 natural size. 



Fig. 99. A, Ungual phalanx, 

 No. 3; B, Ungual phalanx, No. 

 5 — 1/2 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 



