196 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



which on the dorsal side becomes a conspicuous beak ; the distal trochlea 

 is extensively reflected upon both dorsal and palmar faces and describes 

 somewhat more than half a circle ; it consists of two rounded ridges, with 

 a median groove between them ; on the dorsal side of the phalanx, above 

 the distal trochlea, is a deep pit for the beak of the ungual. The second 

 phalanx is of nearly the same length in digits II, III and IV, but is 

 heaviest in III ; in digit V it is much shorter and more slender and the 

 distal trochlea is reduced. 



The ungual phalanges, which differ only in size in the various digits, 

 quite closely resemble those of Megalonyx, being very long, compressed, 

 decurved and sharply pointed, with a shallow cleft at the tip ; the bony 

 hood at the base of the claw has much the same relative development as 

 in the latter, and the subungual process is similar, but somewhat nar- 

 rower, and is pierced by two vascular foramina ; the proximal end is very 

 deeply incised to form a trochlea for the second phalanx and the dorsal 

 border is drawn out into a broad, blunt beak. In the pollex the ungual 

 is less reduced than that of Megalonyx, and in the three median digits is 

 very large, longest in III and somewhat shorter in II than in IV ; in V it 

 is much smaller. 



In length, the three median digits much surpass the laterals I and V, 

 and are of nearly equal lengths, the phalanges compensating for the dif- 

 ferences in the metacarpals. Thus, the longest digit is III, which is due 

 to the size of the ungual, while the larger ungual of II makes it nearly as 

 long as IV despite its much shorter metacarpal. In order of length the 

 digits are as follows : III, IV, II, V, I. In actual length there is hardly 

 any difference between digits III and IV, but the position of the former 

 with reference to the carpus makes it appear to be considerably longer. 



MEASUREMENTS. 



Scapula, breadth distal end over coracoid .068 Radius, width of proximal end 025 



Scapula, anterior-posterior diameter of " " " distal end 030 



glenoid cavity 03 2 Carpus, length in median line 030 



Humerus, length from head 192 " width . . .- 059 



" width of trochlea 044 Metacarpal II, length 038 



" " over epicondyle 079 " " width of proximal end .016 



Ulna, length 197 " " " " distal end 013 



" " of olecranon 035 Metacarpal III, length 038 



" width at sigmoid notch 028 " " width of proximal end .. .023 



Radius, length 165 " " " " distal end 016 



