126 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



premolars. In N. crassus and N. pugnax the crown of the lower canine is more obtusely conical. 



The female lower canine is also a low-crowned delicate tooth, more premolariform than the upper 

 canine. In N. osborni (Amer. Mus. No. 11466) it has a faint internal cingulum continuous with a curved 

 anterior ridge, and it is differentiated from pi chiefly by its much greater size, straighter front edge and 



Fig. 32. Front end of lower jaw of Xufhdn-fu.s pufinn.r, showinu- all four incisors in situ. Viewed from above. Middle 

 Eocene, Lower Bridger beds. X f- 



steeper, flatter posterior face. In A^. matthewi (Amer. Mus. No. 11202) the lower canine, which may 

 well be that of a female, is a small tooth with a vertical single fang; the crown is not caniniform but dis- 

 tantly resembles that of pi; it is markedly asymmetrical, flattened on the inner face, with a very obtuse, 

 gently recurved tip. In an older species A^. nunienus (Amer. Mus. No. 12736) the female canine is less 

 premolariform, with a higher, more pointed crown. In the large species of Pelycodus the canine was 

 nearly as stout as it is in Notharctus but in the very small and primitive P. ralstoni the canine alveolus 

 (Amer. Mus. No. 16093) shows that this tooth was slender. This may very well be a female character. 



Taken by itself, the direct evidence is insufficient to decide whether in the Paleocene ancestors of 

 the Notharctinse the canines were stout and caniniform, or slender and with the crown remotely resem- 

 bhng that of pi. The loss of the third lower incisors at a very early date, however, offers some evidence 

 for the view that they were crowded out by the enlargement of the canines, and the presence in early 

 members of the group of a fairly stout jaw and well-developed muscle crests is compatible with the view 

 that originally the canines were at least much larger than the incisors and anterior premolars. This 

 subject is discussed below, page 200. 



In Ada-pis both the upper and lower canines have shorter, less caniniform crowns than those of male 

 Notharctus. In Adapts parisiensis the canines are sub-premolariform with compressed and cutting rather 

 than piercing crowns, and there is a marked tendency for incisors, canines and premolars to assume a 

 more or less cutting type, with a closed tooth row (loss of diastemata). In Adapis magnus (cf. Stehlin, 

 1912, figs, on pp. 1240, 1243) the upper and lower canines distantly resemble those of the female Notharc- 

 tus but are much thicker; the upper canines are also blunter; the lower canines have the short crown 

 more sharply recurved and the root is very thick; a heavy internal cingulum is present. In Adapis 



