NO. 2 A STUDY OF MENISCOTHERIUM — GAZIN 57 



vex proximal articular surface for the radius, but this does not appear 

 so well faceted farther ventrally nor does it extend relatively so far 

 distally on the dorsal surface. The distal surface for the magnum is 

 more flattened dorsally but exhibits a deep circular concavity on the 

 ventral half for the proximal prominence of the magnum. The 

 more lateral and dorso ventrally concave facet for the unciform faces 

 slightly more laterally and is decidedly narrow and ventrally more 

 restricted than in Meniscotherium. Medially the lunar is slightly con- 

 cave and shows a variably developed facet or facets for the scaphoid. 

 Lateral faceting for the cuneiform is likewise variable and may be 

 restricted to a dorsoventrally elongate zone along the distal portion. 

 The ventral extremity of the Phenacodus lunar presents a somewhat 

 more rounded knob ; a less-flattened protuberance than in Menisco- 

 therium. 



Cuneiform. — The relatively compressed cuneiform is elongate 

 much as the scaphoid, but its long axis is more nearly transverse 

 with its lateral extremity deflected ventrally. The proximal surface 

 shows a dorsoventrally concave and transversely elongate surface for 

 articulation with the ulna. The relatively acute, transversely elon- 

 gate ridge that bounds the concavity ventrally divides the ulnar sur- 

 face from a narrow but transversely somewhat elongate proximoven- 

 tral facet for the pisiform. The facet for the unciform covers the 

 entire transverse portion of the distal surface and is slightly concave 

 dorsoventrally. Transversely a very gentle saddle divides a larger 

 medial portion from a somewhat smaller lateral area. The roughened 

 dorsal surface is distoproximally very shallow laterally but becomes 

 a little deeper medially. The ventral two-thirds of the medial surface 

 is faceted for articulation with the lunar. The ventrally directed 

 lateral extremity is an irregularly flattened prominence that appar- 

 ently does not support any of the pisiform articulation. 



The Phenacodus cuneiform is dorsoventrally as well as proximodis- 

 tally deeper relatively, and the ventrally directed lateral extremity is 

 longer and more massive. The ventrolaterally tapering extension or 

 extremity carries most of the large triangular facet for the pisiform 

 on its steeply sloping proximal surface. The concave proximal artic- 

 ular surface for the ulna is approximately as in Meniscotherium 

 but relatively deeper dorsoventrally. Also the more uniformly con- 

 cave distal facet for the unciform is dorsoventrally deeper relative to 

 its length transversely. The acutely angled medial surface shows a 

 crescentic facet for the lunar adjacent to the arcuate distal margin. 



Pisiform. — The Meniscotherium pisiform is moderately elongate, 



