EDENTATA OF THE SANTA CRUZ BEDS. 129 



proximal row, and is narrow, but very thick palmo-dorsally ; on the ulnar 

 side is an oblique projection, which extends beneath the lunar to a contact 

 with the magnum ; on the distal end is a large, saddle-shaped facet for the 

 trapezoid and a much smaller one for the trapezium. The lunar is low, 

 broad and very thick, with a massive, rugose tubercle projecting from the 

 palmar face ; the radial facet is very convex and descends well upon the 

 dorsal side ; distally, the lunar rests upon the scaphoid and magnum, but 

 has also a small contact with the unciform. The pyramidal is very broad, 

 but not so thick as the lunar, with which it is in close contact ; the facet 

 for the ulna is large and slightly concave, but does not cover the whole 

 proximal end of the bone, being separated by a considerable space from 

 the radial facet of the lunar ; the pisiform facet is a narrow band. The 

 pyramidal rests upon the unciform, but projects externally beyond it and 

 bears a facet for metacarpal V, and on the ulnar border is an additional 

 facet, which was doubtless for just such an accessory ossicle as is found in 

 the manus of Sclerocalyptus. The pisiform most resembles that of Glyp- 

 todon, but is much more slender; it is small, curved and laterally com- 

 pressed, tapering to a blunt point at the free end and transversely ex- 

 panded at the proximal end. The trapezium and trapezoid are not known. 

 The magnum has a small exposed dorsal face, which is of nearly rectan- 

 gular shape ; the proximal end is covered by the lunar and the contact 

 with the scaphoid is entirely lateral ; the distal end has a large, saddle- 

 shaped facet for metacarpal III, and a very small surface for II. The 

 unciform is somewhat smaller than the pyramidal and has but a small 

 palmar tubercle ; distally it is covered almost entirely by the large 

 facet for metacarpal IV, that for V being very small ; metacarpal III also 

 has a contact with the unciform, which is very small dorsally, but grows 

 larger toward the palmar side, being incised in the bone in a curious 

 way. 



No metacarpals of this genus have yet been found and the number of 

 digits is therefore uncertain, but there seems to be no reason to doubt 

 that the manus, like the pes, was pentadactyl. 



The only phalanges of the manus that I have seen are two belonging 

 to the La Plata skeleton, one of which is an ungual ; this is elongate, 

 tapering and bluntly pointed, without cleft at the distal end, and with 

 very massive and rugose subungual process ; in shape it most resembles 

 that of the second digit in the manus of Sclerocalyptus. 



