GREGORY: NOTHAh'CTVS, AN AMERICAN EOCENE PRIMATE 



127 



rutimeyeri (cf. Stehlin, 1912, fig. on p. 1268) the lower canine resembles that of the female of Notharctus 

 matthewi and N. osborni save that the tooth is more recurved, the internal and external cingula are heavier 

 and end posteriorly at the junction with the crista posterior in a low projection. This tooth is also inter- 

 mediate in structure between that of the more specialized Adapis parisiensis and the primitive type pre- 

 served in the American representatives of the family. 



• Fig. 33. I'pper and lower canines of J f/r/jO/.v. X §. After Stehlin. 



Top row: Adapis magmis. Left upper canine: buccal, anterior (mesial), lingual. 

 Middle row: Adapis magmis. Left lower canine: lingual, posterior and buccal views. 

 Bottom row: Adapis rutimeyeri. Right lower canine: lingual, posterior and buccal views. 



Premolars 



The premolars of Notharctus may be divided into three categories : first the very small and simple pi, 

 which are never replaced, erupt with the deciduous teeth, and may be homologous with them; in the 

 upper jaw p^ has only a single root; in the lower jaw pi has either a single root, e. g., Pelycodus trigonodus, 

 N. osborni, tyrmmus, pugnax, crassus, or there is a faint external groove, showing an incipient tendency 

 to divide the root into anterior and posterior moieties {N. venticolus). Second, the intermediate group 

 pi, pi, of which pi are more simple and but little advanced beyond pi, while pi are very distinctly more 

 advanced toward the pattern of p| ; both pi and pi have two principal roots arranged anteroposteriorly 

 and homologous with the two primary roots of the molars ^ ; p'' has also an internal root beneath the 

 inwardly projecting protocone,^ while p3 shows a transverse widening of the posterior part of the crown 



1 On the homologies of these roots, see Gregory, 1916, Bull. Amer. Mus. Nat. Hist., XXXV, p. 246. 



* I apply the name protocone to the main lingual cusp of the premolars for the reasons given in Part I of this series, 1916, Bull. 

 Amer. Mus. Nat. Hist., XXXV, pp. 242-24.5. 



