GREGORY: NOTHARCTdS, AN AMERICAN EOCENE PRIMATE 



form, and parts of metatarsals I and III; No. 13024 (associated with lower jaw and limb bones, referred 

 to N. tenehrosus), right tarsus with parts of metatarsals and phalanges, left calcaneum, astragalus and 

 fragments of phalanges; field number 420 (from near Millersville, Lower Bridger, referred to N. pugnax), 

 left astragalus, calcaneum, cuboid ento- and ectocuneiform, proximal end of metatarsal I. The different 

 species of Notharctus differ in the pes only in size and in minor characters. 



From the pes of the much older and more primitive Pelycodus frugivorus of the Wasatcli, that of 

 Notharctus is distinguished by the lengthening of the lower half of the calcaneum and by the antero- 

 posterior widening of the entocuneiform. From the pes of " Adapis parisiensis," that of Notharctus is 

 distinguished by the much greater length of the lower half of the calcaneum and by the narrowness of 

 the astragalus. (Fig. 21.) 



The pes of Notharctus ofTers important evidence in favor of the view that this animal should be classi- 

 fied under the suborder Lemuroidea rather than under the Anthropoidea as by Wortman (1904, pp. 172- 

 174), since the pes is incontestably lemuroid rather than anthropoid in type. Here, as in other parts 

 of this work, the writer is not opposing the view that Notharctus is structurally ancestral to the South 

 American monkeys, in the pes as well as in all other parts of the skeleton. Such a derivation of the South 

 American monkeys as suggested by both Leidy and Wortman, seems indeed to be very probable. But 

 this does not alter the fact that NotJutrctiis is in a lemuroid stage of evolution in the great majority of 

 its known cliaracters. 



Fig. IS. Left pe.s of J.rjHlnnur >ini.<ifrl!inis, Amer. INIus. No. 81251. Fragments of left pes of "JJo/w.s' jjarislrvsls;' 

 Ainer. Mus. Xo. IOOKk Niitural mzv. 



Broadly speaking, the pes of Notharctus differs from that of the modern Lepilemur chiefly in the 

 much greater length and narrowness of the phalanges, in the stoutness of the metatarsals, and in the 

 more vertical position of the meso- and ectocuneiform. 



In the description of the several elements of the pes which immediately follows, comparisons are 

 made only with Lemur or allied forms. The comparisons with Cehus and other primates are given after- 

 ward (pp. 106, 107). 



