350 Wortman — Studies of Eocene Mammalia in the 



osity by a distinct bicipital groove. The deltoid crest is 

 moderate, but the extent to which it descends upon the shaft 

 can not be determined on account of the imperfect condition 

 of the bone. Upon the whole, its proximal end presents a 

 very strong likeness to that of Cheiromys and Propithecus 

 ainong tlie Primates, and differs from that of the rodents. The 

 distal end is noteworthy for its great proportional breadth. The 

 internal condyle is prominent, as in all early mammals. There is 

 an entepicondylar foramen and an unusually broad supinator 

 ridge. On account of the incompleteness of the latter, it is im- 

 possible to state whether it terminated abruptly above, as in 

 Cheiromys^ or sank gradually away into the shaft, as in Propithe- 

 cios and the other lemurs. The distal articular extremity pre- 

 sents the usual divisions into trochlear and capitellar portions. 

 A characteristic feature of this part of the Primate humerus is a 

 ridge descending from the shaft in front, to become continuous 

 with the external raised edge of the ulnar articular surface. No 

 trace of this ridge is found in the humerus of the Podentia, 

 but in the fossil it is present, although not so strong as in exist- 

 ing lemurs and monkeys. The trochlear portion for articula- 

 tion with the ulna is well rounded and terminates behind in a 

 moderately deep olecranon depression. The capitellar portion 

 is unusually globular and displays upon its outer side a distinct 

 groove which extends somew^hat more than halfway around the 

 articular extremity. 



Among living forms, the only case in which this groove is 

 so well develo]3ed is in Propithecus. Cheiromys^ Galago^ and 

 Cheirogaleus exhibit distinct traces of it, but it is confined to 

 the upper outer edge of the capitellum. In ProjpitlieGus it is 

 associated with a characteristic shape of the articular head of 

 the radius, which consists of a central depression surrounded 

 by a more or less flat ringlike area around the edge. The head 

 of the radius is not preserved in the fossil, but the similarity 

 in the structure of the corresponding humeral articulation 

 leaves little doubt that its form was like that of Propithecus. 

 The distal end of the humerus is thus seen to be like that of 

 the lemurs and entirely different from that of Paramys and 

 Sciicrus^ with which I have compared it. 



The olecranon of the ulna is unusually long, and in this 

 respect differs from all the modern lemurs, as well as from 

 SciuTus. It is deeply grooved upon its outer side and presents 

 an extensive, flattened, subcutaneous area upon its under side. 

 In the first of these characters it resembles the ulna of Propi- 

 thecus^ and in the second that of Cheiromys. The similarity 

 to these two genera also extends to the distal ends of both the 

 ulna and radius. 



