66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



to nearly circular in proximal view and its neck moderately slender 

 and anteromedially directed. The fossa for the ligmentum teres is 

 noticeably posterior in position and essentially marginal, in keeping 

 with the posteriorly directed cotyloid notch of the acetabulum. The 

 greater trochanter is robust and extends proximally a little more than 

 the head, from which it is separated by a well-defined notch. The 

 posterior crest of the greater trochanter partially covers posteriorly a 

 deep and elongate digital fossa into which are inserted the obturator 

 muscles. Distally this comparatively thick or well-rounded crest 

 appears to divide, and a more feeble, sometimes poorly defined crest 

 or intertrochanteric line crosses the shaft distomedially to join the 

 distal extremity of the medially outstanding, nearly triangular lesser 

 trochanter for the iliopsoas on the posteromedial margin of the shaft. 

 The apex of the lesser trochanter has a position about a quarter 

 of the length of the bone distal to the proximal extremity. The 

 better denned lateral portion of the posterior crest from the greater 

 trochanter extends distally to join the prominent and flattened third 

 trochanter, which is almost halfway down the shaft. The develop- 

 ment of this process emphasizes, as in the horse, the importance of 

 the superficial gluteus muscle in abducting the limb and flexing the 

 hip joint. The outline of the third trochanter varies somewhat from 

 a proximodistally elongate flare to a shorter but more laterally pro- 

 jecting prominence. 



< >n the enlarged distal extremity the patellar trochlea is narrow, 

 elongate, and prominently raised. The condyles are large and sepa- 

 rated by a broadly open intercondyloid notch, and the lateral and 

 medial surfaces of the extremity are strongly divergent posteriorly. 

 The condylar tuberosities or epicondyles are noticeable, and the outer, 

 more subdued, is at the extremity of the prominent lateral supra- 

 condyloid crest which extends distally from the third trochanter. A 

 similar medial supracondyloid crest disappears a short distance proxi- 

 mally on the shaft. 



Much that Cope said (1884b, pp. 455-456) about the Phenacodus 

 femur applies to that of M enisc other ium, particularly with regard to 

 the proximal extremity and much of the shaft, but I note that the 

 greater tuberosity in Phenacodus, although anteroposteriorly deeper, 

 is a little less extended proximally, and the shaft is relatively more 

 robust. Distally the fossae at the posterior base of the condyles are 

 much less significant in Meniscotheriam, and the transversely oriented 

 posterior portion of the inner articular surface is as wide as or 

 wider, rather than narrower, than the more oblique or transversely 



