notharctus an eocene lemur 251 



before the skull, the genus would undoubtedly have been placed in the 

 family Lemuridae and even in the subfamily Lemurina?. The meta- 

 podials, astragalus and calcaneum, pelvis, femur, tibia, humerus, forearm, 

 vertebrae, and all other parts preserved are practically identical with 

 those of Lemur. Every process, rugosity, and curve in the Notharctus 

 bones finds its evident homologue in Lemur, so that the myology of the 

 two must have been almost identical. Only the Eocene genus was slightly 

 more primitive, in that the limbs are less elongate. 



The skull of Notharctus has a much smaller brain-case, smaller audi- 

 tory bullae, and a far less specialized dentition. The incisors, canines, 

 and anterior premolars are of primitive type and have not assumed the 

 aberrant and highly characteristic lemurid form. Because its front teeth 

 lack the lemurid modification and because the supposed course of the 

 entocarotid artery and certain details of the lacrimal are not the same 

 as in Lemurs, Doctor Wortmann 9 concluded that Notharctus was not an 

 ancestral Lemur ; but it now appears probable that these differences from 

 Lemurs are merely primitive rather than aberrant characters. So far as 

 I have yet observed, there is only one important character which excludes 

 Notharctus from direct ancestry to the Lemurs. The upper molars in 

 becoming incipiently quadritubercular have departed from the more 

 tritubercular type preserved in the ancestral Pelycodus of the Wasatch 

 and Wind River. Pelycodus is nearer to the ancestors of Lemur; while 

 the allied Pronycticebus of the French Eocene is held by Grandidier 10 to 

 be ancestral to the common Loris (Nycticebus) . A phylogenetic or verti- 

 cal classification would include Pelycodus and Notharctus in the Le- 

 muridae; but a "horizontal" classification, marking stages of evolution, 

 would include Notharctus in the Adapidae, as has been done by Schlosser. 11 

 An examination of skulls, teeth, and limb bones of Adapts and Notharc- 

 tus indicates that Adapts is merely a specialized and aberrant collateral 

 descendant of Notharctus, as held by Schlosser. 



The postcranial skeleton of Notharctus is more primitive than thai 

 of any Platyrhine or Catarhine; Notharctus also retains the right number 

 and kind of incisors, canines, and premolars for an ancestral monkey o( 

 either grand division. However, the occurrence of numerous short- 

 jawed, large-brained Primates in the Wasatch with normal incisors, small 

 canines, tritubercular molars, and reduced premolars suggests the rise 



9 Eocene mammalia in the Marsh collection, Peahody Museum. Part ii, Primates. 

 Amer. Jour. Scl., vol. 15, p. 410. 



10 Les Lemuriens disparus. . . . Nouv. Archiv. du Mus. 4e Ser., Tome vii, 1906, 

 pp. 28-30. 



" Zittels Grundztige der Palliontologie. II. Abt. Vertebrata, L011, p. 647. 



XVIII— Bull. Geol. Soc. Am., Vol. 24, 1912 



