gregoky: xotiiarctus, an American eocene primate 



91 



inner sides respectively. The digital fossa is somewhat less extended vertically than that of Leniur 

 mongoz, this perhaps implying that the obturator internus, gemelli, obturator externus and other adductors 

 of the femur were somewhat less robust than those of Lemur. 



The long shaft of the femur is cylindrical in mid-section and is similar to that of Lemur varius. The 

 shaft as a whole has a .slightly less straight and more irregular contour than that of Lemur. The linea 

 aspera, or adductor ridge, is represented by a long vertical groove running down the posteromedial side 

 of the shaft from below the lesser trochanter to a point about two-thirds the distance down the shaft. 

 About fifteen millimeters below the lesser trochanter the arterial foramen opens in this groove. Traces 

 of such a groove are found in Lemur mongoz and Lemur varius. The groove and the lips on either side 

 of it in Lemur serve for the insertion of the adductor longus muscle. No distinct crest for the insertion 

 of the lower part of the gluteus maximus is present either in Notharctus or in Lemur, although in the latter 

 this muscle is widely extended from the third trochanter downward to near the lower end of the shaft. 

 The popliteal surface on the back of the shaft above the condyles resembles that of Lemur. 



The distal end of the femur is relatively smaller than that of Lemur varius; the external condylar 

 ridge or keel is a little more protuberant and is slightly less reflected on to the front face of the femui-; 

 the patellar facet is narrower; the external tuberosity is a little more prominent, and the whole distal 

 portion of the femur is a little less synnnetrical than it is in Lemur. The intercondylic notch is narrower; 

 nevertheless a close comparison of the articular relations of the femur, tibia, and patella in Notharctus 

 and Lemur leads to the conclusion that there was little difference in the range of flexion and extension 

 at the knee, that of Lemur being perhaps a little greater. 



Thus the general resemblance of the femur of N'otharctus to that of Lemur is so sti'ong that we may 

 be quite sure that the arrangement of the muscles was substantially identical in the two animals, the 

 differences being mostly differences of proportion. With regard to the normal perching pose of the hind 

 limb, Lemur may ordinarily abduct the thighs a little more than did Notharctus, and in leaping it may 

 have extended the leg a little more, but on the whole the postures and movements of the limb of Notharc- 

 tus were extremely Le/?;m--like. 



The femur is also fairly similar to that of Lepilonur mustilenu.'i, with which it has freciuently been 

 compared during the course of this study; it differs only in the pi'oportions of cei-tain parts whicli need 

 not be specified. 



The femur of Adapts is even closer in appearance to that of Notharctus than is the femur of Leinur, 

 as may be seen in the accompanying figures. The lesser trochanter is e\'en more pointed than thai of 

 Notharctus, the third trochanter is a little less prominent. (Figs. 15, 1(5.) 



Comparative Measurements of the Femur 





A'', osborrii 



A^. leiu'hrosii.-^ 



L. mongoz 



L. mongoz 



L. rorim 







No. 11474 



No. 1727 



No. 31254 



No. 228S6 



Xo. is;)4i) 



No. ;!()2:)() 



Total Length of Femur 



122. 



138. 



122. 



128. 



1.52. 



145. 



Greatest Diameter of Proximal End, 















head to greatest trochanter 



20 



24. 







29 





Greatest Diameter of Distal End 



1(5. 3 



19. 





17. .3 





21 . 



The femur of Propithecus is fundamentally similar to that of Notharctus, but more specialized. The 

 shaft is longer and more circular in section, the second trochantec is more expanded, the head more globu- 



