ART. 1. Pm MATES OF THE FORT UNION GIDLEY. 27 



American monkeys and the Anthropoidea in general, namely, about 

 40°. In the Madagascar lemurs, even in such divergent forms as 

 Microccbus and Dauhentonia, this angle is diminished by nearly one- 

 half, bringing the head closer to the shaft in the lemurs than in 

 Notharctus and the Anthropoidea. This feature denotes a similarity 

 between Notharctus and the anthropoids in the angulation of the 

 scapula with the humerus, which is not shared by the lemurs. 



One other important feature of the humerus remains to be con- 

 sidered, namely the modifications of the distal end. In his table of 

 comparisons between the humerus of Notharctus and those of the 

 anthropoid apes and man, Gregory has noted that the capitellum is 

 *' ball-like in center, produced externally toward very inconspicuous 

 external epicondyle" and that the trochlea is not grooved. The first 

 of these distinctions is not quite clear, since the figures given by 

 Gregory as well as the cast in hand indicate a very conspicuous ex- 

 ternal epicondyle. But the important obervation in this connection 

 would seem to be that the capitellum is but slightly more globular 

 or " ball-like" than that of the South American monkeys, is decidedly 

 more rounded externally than in many of the lemurs; and, with the 

 diminishing of the supinator ridge, which would bring the epicondyle 

 closer in, the modification to the condition found in the Platyrrhine 

 monkeys would readily be accomplished. From the Notharctus stage 

 to such a modification as that observed in the African lemur Pe- 

 rodicticus potto, in which there is a well-developed additional external 

 groove and ridge not found among the Anthropoidae, the transition 

 would be far more difficult. This feature in Perodicticus is indicated 

 in the less progressive humerus of Lepidolemur, and is the more sig- 

 nificant since between the humeri of the two lemurs just mentioned, 

 there is about the same degree of progressive development as between 

 those of Notharctus and Alouatta or Hapale, the Madagascar lemurs 

 being nearer the stage of Notharctus with its broadly expanded supi- 

 nator ridge and well-developed entepicondylar foramen, the conti- 

 nental lemur approximating the Platyrrhines just named in having 

 no entepicondylar foramen, and having a greatly diminished supi- 

 nator ridge. 



Regarding the absence in Northarctvs of the trochlear groove, this 

 also is conspicuously absent in Alouatta, and absent or but shghtly 

 indicated in the other South American monkeys. 



Still another anthropoid and nonlemurine feature of the Notharctus 

 humerus is observed in the very pronounced upward sloping of the 

 trochlear toward the base of the capitellum. This feature is also 

 very marked in Alouatta. 



Continuing with the radius and ulna, again Gregory has emphasized 

 the special likeness of these elements to those of the lemurs, but 

 many of the differences pointed out by him in comparing them with 



