172 THE DESEADO FORMATION OF PATAGONIA 



The humerus is a very characteristic bone, short and 

 stout, but greatly flattened from front to back. It has 

 a large sessile head, which is strongly convex, and projects 

 internally over the margin of the shaft. The external 

 tuberosity is large and rugose but does not project above 

 the level of the head. The deltoid ridge is shifted to the 

 external side of the bone, and makes a long, muscular 

 ridge, while on the opposite external margin is a second 

 ridge, and between the first and second ridges a long furrow 

 or trough is inclosed. These terminate just below the 

 middle of the bone in roughened bosses, which all but meet. 

 The epicondyles are large and give the excessive width 

 to the bone. The external condyle is prolonged upward 

 and ends in a spur. The trochlea is of moderate width 

 and gently undulated. The supratrochear fossa is only 

 slightly depressed, and the anconeal fossa is likewise 

 shallow. The bone has no exact counterpart, but is simi- 

 lar to that of Moeritherium and Palaeomastodon, but in 

 each case is more flattened and has the external ridges more 

 developed. 



Gaudry describes the radius and ulna. They are 

 ridiculously short, and very massive. The ulna is stout 

 with a massive olecranon which is directed well toward the 

 rear. The sigmoid notch is shallow, the coronoid process 

 short, and the articular area expanded so that the ulna 

 covers the whole of the posterior of the trochlea of the 

 humerus. The upper end of the radius is compressed 

 antero-posteriorly, but distally it expands into a heavy 

 bone. Its upper articulation is expanded, so that it comes 

 in contact with the full width of the anterior portion of 

 the trochlea of the humerus. 



The carpus and front foot are of questionable associa- 

 tion. Ameghino described a front foot as P. romeri, and 

 later Tournouer assigned this foot to Astrapotheriam. 

 However, I have seen no reason to think it belongs to 

 Astrapotherium, being far too small, and so would for 



