EDENTATA OF THE SANTA CRUZ BEDS. 193 



tinues to widen to the distal end ; the ulnar border describes a regular, 

 slightly concave curve, beginning below the bicipital tubercle, which is 

 large, prominent and rugose, placed well below the head and on the pos- 

 terior side of the shaft. The distal end of the radius is moderately wide 

 and thick and has a large, low tuberosity on the dorsal face ; the carpal 

 surface is concave, undivided and oblique to the shaft, descending to the 

 styloid process. 



The manus (Plate XXXIII, fig. 2) is much less specialized than in any 

 of the known Pleistocene genera, most resembling that of Megalonyx. 

 All of the carpal elements are separate from one another. The scaphoid 

 is very short proximo-distally, but very broad ; on the ulnar border it is 

 thick, but contracts much to the radial side, where it is extended into a 

 blunt, hook-like and slightly recurved process ; the radial facet is reflected 

 far over upon the dorsal face, extending to and making a sharp angle 

 with the surface for the trapezoid ; on the distal end are large facets for 

 the trapezium and trapezoid and, on the palmar side, one for the lunar 

 also ; contact with the magnum is extremely limited, while in Megalonyx 

 it is quite extensive. 



The lunar is large and shaped quite as in Nothrotherium, but 

 with the radial facet much more extended upon the dorsal side. On 

 the palmar side the lunar extends beneath the scaphoid and on the 

 ulnar side has a very large, deeply concave facet for the pyramidal ; 

 distally, the lunar rests entirely upon the magnum and has no contact 

 with the unciform. 



The pyramidal is large and of irregularly cubical shape ; it is longer 

 proximo-distally than the scaphoid or lunar, but diminishes toward the 

 ulnar border ; the ulnar facet is large, somewhat saddle-shaped and forms 

 almost a right angle with the surface for the pisiform, which is entirely 

 palmar ; on the radial side the pyramidal extends beneath the lunar, much 

 as in Megalonyx. 



The pisiform is large and laterally compressed, and somewhat resem- 

 bles that of Megalonyx, but is of more nearly circular form. 



As in Nothrotherium, the trapezium is free, while in the other Pleisto- 

 cene genera it is fused with the scaphoid ; it is long, very narrow and 

 thick, and distally articulates only with metacarpal II. When placed in 

 its natural position, the obliquity of the trapezium is such as to suggest 

 that the pollex diverged considerably from the other digits. 



