GREGORY: NOTIIARCTUS, AN AMERICAN EOCENE PRIMATE 



93 



its anterior surface and is inserted on its outer margin. The front of the shaft of the tibia is flatter 

 in Notharctus. The distal end of the tibia is narrower than that in Lernur varius, but not much different 

 from that of Lemur mongoz. As in other primates the internal malleolus ends below in a prominent hook. 

 The cnemial or anterior tuberosity is much higher and narrower and terminates abo\'e in a sharp spine. 

 This condition is correlated with the narrower intercondylic notch and narrower distal end of the femur. 



• I t f 



1 2 3 4 



V\'^. 17. ( 'oiiiparativc (ijiurc's: rinht tiliia, fibula, and patella otWof/farr/z/.s- and Lniiiir. Natural si/,c. 



1. Notharctus osboriii. Amer. Mus. No. 11474. Front view. 



2. Lemur niongoz. Amer. Mus. No. 22886. Front view. 



3. 4. The same specimens, back view. 



The tibia of Notharctus tenebrosus, No. 1727, is much longer than that of N. oshorni, and is as long 

 as that of Lemur mongoz, but much stouter. The stoutness of the tibia and bowing apart of the tibia 

 and fibula imply a corresponding development of the muscles of the leg and foot and, in fact, the feet 

 are relatively large. 



In general, the tibia of Notharctus is essentially lemurine, differing chiefly in its more robust character. 



