200 



GREGORY: NOTHAltCTUS, AN AMERICAN EOCENE PRIMATE 



the " Vordergebiss " of Adapts "kurzweg als primitiv." He said only that the small insectivorous forms 

 of the genus Pelycodus have the primitive dental formula of if, Ci, P|, M| (1915, p. 439) and that Noth- 

 arctus had not assumed the lemurid specialization of the incisors, canines and anterior premolars (p. 425). 



Three possible views may be held as to the exact character of the canines in the common ancestors 

 of the Notharctinse and Adapinse: 



(1) they may have been subcaniniform as they are in the males of Pelycodus frugivorus; 



(2) they may have conformed to the description of the primitive primate canines given by Dr. 

 Stehlin (1916, p. 1530): "urspriinghch nicht verstarkt und caniniform, sondern brachyodont 

 und structurell ein Mittelding zwischen vordern Praemolaren und hinteren Incisiven;" 



(3) they may have been somewhat between (1) and (2), but nearer to (1), as in the canines of the 

 female of N. osborni. 



In Ada-pis parisiensis the upper canines and the first three premolars are more or less similar in form 

 and they are crowded together into a continuous series, with sharp cutting edges and marked internal 

 cingula; the incisors are very compressed and trenchant. In the lower jaw the canines have a short 

 low crown of sub-premolariform shape, the premolars are crowded and the incisors have wide-edged 

 crowns. This condition of the front teeth is associated with a fairly advanced stage in the evolution of 

 the posterior premolars and molars and with the inferred habit of eating fruit covered with resistant 

 fibrous rinds. The writer believes that this condition is decidedly more specialized than that of the 

 Notharctinae, especially the early forms (see pages 124-127), in which the incisors were of small size, with 

 not widely expanded tips, the canines neither fully caniniform or premolariform, but much larger than the 

 incisors and anterior premolars, the first premolars very small and separated by a diastema from the 

 canines. These conditions were approached in Adapts sciureus (cf. Stehlin, 1916, p. 1515, fig.) which 



Fig. 75. Lower jaw s of Jr/a^j/s. Natural size. After Stehlin. 



1. Adapis sciureus. Lower Eocene (Lutetien), Egerkingen, Switzerland. 



2. Adapis priscus. Lower Eocene (Lutetien), Egerkingen, Switzerkind. 



3. Adapis parisiensis. Phosphorites (? Middle Eocene), France. 



is older than the typical species of Adapis and in the opinion of the writer is much more primitive. In 

 this very small and primitive species, the lower incisors as shown by their alveoli were small, the canines 

 were relatively large, single-fanged, straight-crowned, upstanding teeth, with an obtusely conical tip, 

 a strong internal cingulum and well-marked crista anterior; the crown is widened at the base much more 



