1 94 Bnlletin American Museum of Natural History. [Vol. XVI, 



especially Nos. 55, 65, 4174, 4182, Amer. Mus.); the upper 

 molars are strictly tritubercular, with little or no indication 

 of a mesostyle. This is certainly a very primitive species 

 and it probably comes from the lower levels of the Wasatch 

 beds. Inf. ms = iS-5- 



(Sp. 43) Pelycodus tutus Cope. — This, on the contrary, is 

 the largest (inf. m. series=i7.5 mm.), most progressive, and 

 most abundant species. The superior molars are triangular 

 in form but show a well developed hypocone forming a double 

 internal lobe, but no mesostyle (see No. 4162, Am. Mus.). 

 The paraconid, which is always the first primitive element to 

 disappear among the Primates, shows every stage of position 

 and development; it sometimes appears on nij — nig, but is- 

 alwa3^s distinct on m, . 



P-3 pA m.l m.2 m.3 



Fig. 22. Pelycodus nunienus. Type. 

 Am. Mus. Cope, No. 4734. 



Genus NOTHARCTUS Leidy. 



2. Wind River (Lutetien) Stage. 



As we might expect, in the Wind River specimens the tirst 

 lower premolar is always single fanged, while in the superior 

 molars the hypocone is decidedly more prominent so that in 

 some cases they might be described as quadrate and sexi- 

 cuspidate; a very conspicuous difference is the presence of 

 the mesostyle (Fig. 20). The Wind River species are also 

 generally distinguished by the more advanced transformation 

 of the posterior premolars. As observed by Matthew, the Wind 

 River species show closer affinities to those of the Bridger. In 

 fact the Wind River specimens may well be referred to the 

 Bridger genus Notharctus as characterized below. Cope was 

 entirely mistaken in identifying the progressive Wind River 

 species with the older Wasatch species {P. jarrovii and P. 

 tutus) . 



