NO. 2 A STUDY OF MENISCOTHERIUM GAZIN 6j 



more convex outer articular surface in M eniscotherium. The patellar 

 trochlea in Phenacodus seems broad, and the patella itself is compara- 

 tively wide and not so elongate and distally tapering as in Menisco- 

 therium (see pi. 8) . 



The straight or but slightly curved Hyopsodus femur is slender, 

 elongate, and somewhat flattened anteroposteriorly. The proximal 

 extremity is transversely narrow, as the head and slender neck do 

 not extend medially so noticeably as in M eniscotherium. The head, 

 moreover, is nearly spherical and the fossa for the ligmentum teres 

 is centrally located, well removed from the margin of the articular 

 surface. The greater tuberosity is comparatively small and does not 

 project proximally as far as the head. The digital fossa is proximo- 

 distally much shorter than in M eniscotherium, and the lesser tuber- 

 osity is nearer the proximal extremity. The lateral margin of the 

 shaft from the greater tuberosity to the lateral condyle is compressed, 

 and just beyond to the midpoint of the shaft is laterally expanded into 

 a well-defined, proximodistally elongate third trochanter, with a rugged 

 crest for the superficial gluteus muscle. The distal extremity of the 

 Hyopsodus femur at hand is poorly preserved, but I note that the 

 patellar trochlea is relatively broader than in M eniscotherium. 



TIBIA 



The M eniscotherium tibia is a little shorter than the humerus. 

 It is relatively slender and noticeably bowed anteriorly (see pi. 9). 

 It exhibits an elongate cnemial crest that is laterally deflected and 

 extends straight nearly half the length of the shaft. The crest is 

 distally somewhat roughened, evidently for the tendon of the semi- 

 tendinous muscle which would have its origin at the prominent ischial 

 tuberosity. From this point the crest rapidly subsides as a well- 

 rounded ridge or margin crossing obliquely to the medial side and 

 then directed more or less subdued toward the inner malleolus. 

 Proximally the shaft shows a broad, gently convex anteromedial sur- 

 face and narrower, concave lateral and posterior surfaces which are 

 separated by a sharp posteromedial crest that would support the 

 interosseous membrane. This crest curves strongly outward proxi- 

 mally to where it reaches the facet for the head of the fibula and 

 distally swings somewhat forward and subdued to a more medial 

 position at the place of contact for the distal extremity of the fibula. 

 The posteromedial margin of the shaft is also acute proximally, 

 beneath the medial tuberosity or condyle of the tibia but loses this 



