58 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



The scapula (PI. XI, fig. i) is short and quite broad and the spine is so 

 placed that the prescapular fossa is considerably larger than the post- 

 scapular, and the whole blade is relatively shorter, broader and more 

 rounded than in Diadiaphorus. The neck is broad and there is no 

 distinct coraco-scapular notch ; the glenoid cavity is of a somewhat pecu- 

 liar shape, contracting to a point anteriorly ; the coracoid is not known, 

 but appears to have been small. The coracoid border curves forward 

 strongly in ascending from the neck to the widest part of the blade, which 

 is about the middle of the proximo-distal height, thence curving backward 

 and upward to the suprascapular border : the glenoid border is straight. 

 The spine rises steeply and is somewhat recurved, with convex anterior 

 face, ending distally in a short acromion : the single metacromion is a 

 prominent triangular process, placed just above the acromion, and appears 

 to have been distinctly larger and more prominent than in Diadiaphor^ls. 

 This scapula differs very strikingly from that of TJieosodon (q. v.). 



The humerus (PI. XI, fig. 2) is almost exactly like that of DiadiapJioriis 

 on a smaller scale : it is short and rather slender, the deltoid ridge is 

 obscurely marked and the distal trochlea is of a simple, pulley-like shape. 



Although the ulna and radius are not fused at any point, they are in 

 contact with each other for nearly their entire length, so that there is 

 hardly any radio-cubital arcade. The radius (PI. XI, figs. 2, 10) is short, 

 somewhat shorter than the humerus ; the shaft is slender, of oval cross- 

 section, but somewhat irregular in shape. The ulna (PI. XI, fig. 3) is 

 hardly reduced at all and is nearly as thick as the radius ; its distal end is 

 compressed and plate-like and, in addition to the surfaces for the pyramidal 

 and pisiform, has a small, though distinct facet for the lunar. 



The carpus (PL XI, figs. 9, 9^) closely resembles that of Diadiaphonis 

 in the shape and mutual connections of its various elements, but there are 

 many minor differences. The scaphoid is higher proximo-distally in pro- 

 portion to its width ; the dorsal convexity of the radial facet is more 

 sharply defined and the trapezoid facet incises the bone more deeply ; the 

 facet for the trapezium is relatively very large. The lunar is proportion- 

 ately higher and narrower; its proximal surface is similarly oblique, 

 descending steeply toward the radial side, and the facet for the ulna, 

 though very small, is much more distinct, while the knob-like protuber- 

 ance from the palmar face is smaller. Except for its smaller size, the 

 pyramidal is almost exactly as in Diadiaphoms, but the facet for the ulna 



