GREGORY: 



NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



147 



in front of the posterior extension of the condyle. (Plate XXXVI.) The alveolar foramen is well 

 shown in N. venticolus (Amer. Mus. No. 14655). (Fig. 45.) The foramen is located about 7 mm. be- 

 hind nis and about 5 mm, below the ridge that bounds the temporal area below. From the foramen a 

 straight groove leads upward and backward, marking the course of the inferior dental nerve and vessels. 

 This groove is clearly defined in certain specimens of Adapts (Amer. Mus. No. 10007). (Plate XLI.) 



Behind the symphysis and immediately above the lower border is a pair of shallow pits which proba- 

 bly mark the insertion of the geniohyoid muscles. (Fig. 45.) The corresponding pits in A (iapis parisiensis 

 (Amer. Mus. Nos. 10007, 10013) are defined below by a sharp rim. (Plate XLI.) 



Fig. 45. Left mandibular ramus of Notharctus vcnticolufi. Amer. Mus. No. 14655. Lower Eocene (Lost Cabin beds), 

 Wyoming. Medial aspect. Natural size. 



Fig. 46. Left mandilnilar ramus of Jr/rt/i/,v y;«/7.s;(7/.y/.^. After Stehlin. Medial aspect. Natural size. 



Mental Foramina 



The position of the "mental foramina" has been examined in the following specimens of Notharctinae 

 and Adapinse; 



Pelycodus ralstoni A. 



M. X. H. Xo. 



16093 



Xofharrfus m.sfratus A. M. N. H. 1. 



" trigonodus 





1.5036 



pug,ia.v A. M. N. H. No. 11461 



" frugivorus 





16852 



" 11482 



" jarrovii 





15624 



" 12575 



Notharctus nunienus 





12736 



rraxxu.s " " 12.581 



" Tcnticol us 





146.55 



Jilapis xciin-rns (Stehlin, 1916, p. 1515) 



" matthnci 





42011 



" parlslnisls A. M. N. H. No. 10008 







13030 



" 10006 



" osborni 





1146(;rt. 

 " 1. 



" 10013 



" tenehrosus V. S. N. M. 





" magnvs " " 10511 



" rostratus A. M. N. H. rt. 







