144 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



Adapts priscus (Stehlin, 1916, p. 1511, fig. 366) the protolophid is narrow transversely, the talonid broad, 

 the hypoconid very large, entoconid large, hypoconulid short. M3 in Adapts riititneyeri (idem, Taf. 

 xxi) suggests A. tnagtius but lacks the metacristid ; hypoconulid very small, entoconid low. 



Thus, all the Adapinse differ from the Notharctinse in the oblique position and progressive promi- 

 nence of the protolophid, in the progressive development of a metacristid, in the relatively large size of 

 the hypoconid, reduction of the entoconid and narrowness of the hypoconulid. 



In the Adapinse the interlocking relations of mf have been studied from specimens Nos. 10001-10017 

 (Adapis parisiensis) and 10511 {A. magnus). There was evidently less transverse movement of the 

 mandible than in the Notharctinse. The principal cutting was done by the sharp protoloph and pro- 

 tolophid; the sharp cones and crests easily pierced the relatively tough vegetation. (Plate XXXIX.) 



The final summary of the evolution of the dentition in the Notharctinse and in the Adapinse may be 

 deferred until after the mandible has been described. 



Mandible 

 Plates XXXVI-XLIl; Text Fius. 42-4.T 



The lower jaw in the Notharctinse is fairly stout, but of slight to moderate depth. No very marked 

 differences are apparent between the earlier and the later types, except that in the later species of Notharc- 

 tus the opposite rami coalesce at the symphysis in old animals, leaving, however, a visible suture on the 

 lower border of the chin. There is a wide range of variation in the depth of the ramus, which in N. venti- 

 colus (old male), osborni, AL tyrannus is relatively deep, in N. affinis, N. pugnax, N. crassus quite shal- 



1 2 .3 



Fig. 42, Comparative figures: mandiljular condyles of Nofharcfus and Adapts. Rear view. Twice natural size. 



1. Notharctus osborni. Amer. Mus. No. 11466. 



2. Notharctus crassus. Amer. Mus. No. 12588. - 



3. Adapis parisiensis. Amer. Mus. No. 10007, 



low. The chin also is sometimes very shallow (A^. rostratus), sometimes deep (A^. osborni), and it is not 

 apparent that these differences are either sexual or specific ; for both shallow and deep j aws are sometimes 

 assigned to the same species (e. g., A. tyrannus) on account of the close agreement in the teeth, and again 



