68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



character distally, near the midpoint of the shaft. Distally, the shaft 

 is slender and essentially rounded. 



The proximal extremity of the tibia is broad and laterally over- 

 hanging. The two surfaces for the femur appear roughly equal. 

 The medial surface is somewhat concave transversely but distally 

 offset and broad posteriorly. Along the posterolateral margin of 

 this there is a noticeable facet, offset or obliquely turned from the 

 foregoing and adjacent to the popliteal notch, for attachment of the 

 posterior crucial ligament. The outer surface for the femur rides 

 smoothly up the median spine which forms the medial apex of the 

 surface and accords with the transversely more oblique appearance 

 of the outer articular condyle of the femur. The distal surface of 

 the laterally overhanging outer condyle shows a small, convex, oval 

 and almost distally facing facet for the fibula. On the anterior 

 portion of the proximal extremity there is a distinct transverse notch 

 or step which tends to define the proximal extremity of the cnemial 

 crest and is evidently the position for attachment of the patellar 

 ligament. 



The distal extremity of the tibia is somewhat enlarged and exhibits 

 a pronounced distal extension medially of the internal malleolus 

 which articulates with the inner side of the astragalus. The distal 

 articular surface shows a shallow, anteroposteriorly elongate con- 

 cavity adjacent to the inner malleolus for the inner crest of the astrag- 

 alus. The transversely more elongate outer surface for the medial 

 side of the outer crest of the astragalus is decidedly oblique to the 

 longitudinal axis of the shaft. This oblique facet terminates proximo- 

 laterally adjacent to the fibular contact. 



Cope (1884b, pp. 503-504) has called attention to several differ- 

 ences between the tibia of Meniscotherivm and that of Phenacodus. 

 In the character of the cnemial crest, he noted that it is relatively 

 shorter and more obliquely truncated proximally, and its distal exten- 

 sion does not cross to the internal malleolus in Phenacodus. With 

 regard to "the early disappearance of the external posterior angle 

 and its reappearance on the distal two-fifths of the length of the 

 shaft" in Meniscoth* rium, I suspect that his specimen was unusual 

 or defectively preserved, as seems evident in his illustration (1884b, 

 pi. 25g, figs. 16, a, b, and c). His fifth point evidently refers to the 

 disappearance on the middle of the shaft of the posterior inner angle, 

 rather than the posterior external angle, because as actually stated 

 this was part of his fourth point. He further noted that the posterior 

 face of the shaft distally is roughened for muscular insertion in 



