GREGORY: KOTIIMH'Tl'S, AN AMERICAN EGCENE PRIMATE 



89 



considerably elongate, the femur- is only a little longer than that of Nothiirdm. Tlie hiunero-fenioi-al 

 ratio of Notharctus osborni is .60, as compai'ed with .65 in Lemur rarius, .75 in ( 'ehus m pud n its, and 1.05 

 in Brachyteles arachnoides. The progressive elongation of the humerus in this series is in harmony wilh 

 the crouching position normally assumed by Notharctus as inferred from other exidence, in contrast with 

 the upward slope of the backbone in the normal jiose of Brachyteles. 



The head of the femur is smaller and much less ball-like than that of Lentur; it is located somewhat 

 more in line with the long axis of the shaft, whereas in Lemur it is more sharply set off from and inclin(Ml 

 to the axis of the shaft. The head is thus somewhat more sessile and the neck less constricted. When 



the pelvis and the femur are placed in their normal articular relations it is seen that, in the resting pose, 

 the femur of Notharctus was held out from the body at only a gentle angle, whereas in Lemur the femur 

 is more abducted. Here, therefore, as in so many other characteristics, Notharctus represents a less 

 advanced stage of arboreal adaptation. In Lepilemur the head of the femur is extended further inward 

 toward the digital fossa on the posterior side of the femur than is the case in Notluirclus. In Lcpllcinur 



