422 W. K. GREGORY NOTHARCTUS AND LEMUROIDEA 



is the close agreement between Adopis and Notharctus in the form and 

 relations of the I'acrymal. In both genera the lacrymal was largely 

 within tlio orbit, instead of being widely extended on the face, as it is in 

 Lemurs, and the lacrymal foramen was marginal, instead of preorbital; 

 and this condition is, I believe, the primitive one for Primates in general, 

 the existing Lemurs having lost this and other primitive lemuroid char- 

 acters. The generic difEerences are obvious and may be passed over. 



In the architecture of the skull Adapis and Notharctus reveal differ- 

 ences which are chiefly quantitative, or allometric. In a skull of Noth- 

 arctus in the American Museum (number 11477), the basicranial region 

 has been skilfully freed from the matrix by Mr. Anderson. It exhibits 

 the following important characters: (1) the pterygoid plate of the 

 alisphenoid is continued down outside the bulla; (2) the bulla represents 

 an expansion of the periotic; (3) the auditory prominence or cochlea 

 bears on its outer surface a bony canal for the internal carotid artery ; 

 (4) this canal runs forward to the anterior end of the bulla, and there 

 it enters the posterior part of the basisphenoid ; (5) the entrance to the 

 carotid canal, or posterior carotid foramen, is at the postero-external 

 corner of the bulla; (6) immediately external to the posterior carotid 

 foramen is the stylomastoid foramen, for the seventh nerve. 



In Adapis. as figured by Stehlin (1912), the basicranial region is 

 fundamentally similar to that of Notharctus. Here the pterygoid plate 

 of the alisphenoid likevnse extends outside the bulla, which is again only 

 an expanded portion of the periotic; the cochlea has the same carotid 

 canal, which also runs forward to the anterior end of the tympanic 

 chamber; the stylomastoid foramen is in the same position. Stehlin 

 found preserved in some specimens the delicate tympanic annulus which, 

 as in Notharctus and all other true lemuriform lemuroids, was inside the 

 expanded bulla. 



The dentition, however, offers divergent characters. The upper in- 

 cisors of Adapis are more chisel-like than those of Notharctus, the pre- 

 molars are more compressed, the molars are tritubercular, the postero- 

 internal cusps of the molars are formed by the upgrowth of the basal 

 cingulum, and there is no median external cusp, or mesostvle. 



In Notharctus, on the other hand, tlie jjosterior premolars are wider 

 transversely, the posterointernal cusp of the molars is formed by a 

 splitting or division of the protocone, and there is a. progressively de- 

 veloped mesostyle. 



The different modes of forming the posterointernal cusp of the upper 

 molars are correlated with equal differences in the entoconid in the lower 

 molars. By fitting the upper and lower teeth together I find that in the 



