34 THE DESEADO FORMATION OF PATAGONIA 



The radius and ulna were from another specimen which, 

 however, was associated with a typical astragulus. The 

 two bones are long, slender, strongly curved, and in con- 

 tact with each other throughout their entire length, so 

 that there could have been no rotary movement of the fore- 

 arm. The radius is a slender bone with the proximal 

 articular facet relatively small, the facet being slightly 

 concave, of ovoid outline and with the transverse diameter 

 the greater. There is but a tiny band-like facet for the 

 ulna situated on the posterior side near the inner margin. 

 Distally, the radius widens into a heavy end with a rugose 

 area on the outer side for contact with the ulna, and with 

 two distal facets, a larger for the scaphoid, and a smaller 

 for the lunar, the two being separated by a low ridge. 



The ulna is heavier above, with a strong backwardly 

 directed olecranon process. The sigmoid notch makes 

 almost a semicircle^ the articular surface being broad and 

 extending well onto either side of the bone. The facets 

 for the radius are tiny. The distal end of this bone is 

 wanting. 



MEASUREMENTS, SPECIMEN No. 3275 

 Radius, length 251 mm. 



greatest width at proximal end 28 mm. 



greatest width at distal end 36mm. 



least diameter of shaft 16 mm. 



The femur belongs to the type specimen which is about 

 5% larger than the other specimens. This bone is long 

 and rather slender, with the greater trochanter rising well 

 above the head, which is rounded, on a short neck, and 

 has the ligamentary pit on the posterior margin. The 

 thick, rugose, greater trochanter bends in over the head 

 at its upper end. The lesser trochanter is relatively small, 

 and prolonged into a ridge. Unfortunately the third tro- 

 chanter is broken off in my specimen. The digital fossa 

 is extremely large and deep. Proximally the shaft is 

 flattened, but becomes rounded distally. Just above the 



