184 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



Subfamily Adapinae 

 Lower, Middle and Upper Eocene, Europe. 



Upper molars tritubercular with cingulum-hypocone, no mesostyle; lower molars without paraconids 

 and usually without hypoconulids (except mi), talonids often enlarged; protolophid crest sharp, oblique. 

 Fourth upper premolar early acquiring a posteroexternal cusp; fourth lower premolar with well devel- 

 oped talonid. Incisors typically wide-edged, trenchant; canines straight, dagger-like. Mandible 

 typically short and very stout ^ with greatly expanded angle, condyle gently convex or flattened, coronoid 

 recurved; symphysis coossified. Sagittal and lambdoidal crests high, pterygoid fossae typically wide; 

 mastoid exposure on occiput wide above. 



Subfamily Notharctinae 



Lower and Middle Eocene, North America. 



Posterointernal (pseudohypocone) cusps of upper molars progressively arising from a ridge connected 

 with the protocone, cingulum-hypocone not developed (except rarely on m3) ; m^-nr^ progressively 

 acquiring a mesostyle (incipient in earlier species). Fourth upper premolar with retarded evolution of 

 the posteroexternal cusp; fourth lower premolar with retarded talonid; lower incisors small; canines 

 progressively more or less caniniform, especially in males. Lower molars primitively with paraconids 

 located immediately in front of the metaconids; these are frequently lost, while a central median cusp 

 (pseudoparaconid) may be developed. Mandible elongate, angle forming a long backwardly produced 

 apophysis; symphysis mandibuli primitively not coossified. Condyle transversely convex with a medial 

 inferior prolongation; coronoid high, erect. Pterygoid, or hamular, fossa? narrow; mastoid exposure 

 on occiput narrow above. 



Genus Pelycodus Cope 



Pseudohypocone (jjosterointernal cusp) of m^ nr incipient or not well distinguished from protocone, 

 contour of upper molars trigonal or not entirely quadrate; mesostyles incipient or small; symphysial 

 suture of mandible distinct. 



Genus Notharctus Leidy 



Pseudohypocone of m\ nr prominent, well distinguished from protocone and more or less nearly 

 equal to it; mesostyle clearly distinct; symphysis of mandible co-ossified in old animals. 



The species of Notharctus for the most part have been founded upon incomplete specimens of lower 

 jaws and teeth; they have recently been revised for systematic purposes by Granger and Gregory,- and 

 are considered rather from a morphological viewpoint in present memoir. They exhibit a fairly wide 

 range of size and progressive emphasis of the generic characters. The older species from the Wind River 

 Basin (summit of the Lower Eocene) connect Notharctus with the more primitive and ancestral genus 

 Pelycodus. The latest species, N. crassus, from the Upper Bridger horizons (late Middle Eocene) is an 

 advanced stage of evolution, in which the upper molars have large mesostyles and very distinct postero- 

 internal cusps. The family is apparently represented in the Upper Eocene by the dwarfed and little- 

 known form named '^Notharctus uintanus, which is the last known survivor of the race, unless, indeed, the 

 South American primates were derived from this subfamily (see pages 217-221). 



' Except Ada pis sciureus. 



2 1917, Bull. Amer. Mus. Nat. Hist., XXXVII, pp. 811-859. 



