424 W. K. GREGORY— XOTHARCTUS AND LEMUROIDEA 



the Tndrisinas. With the expansion of the angle, the areas of insertion 

 of the pterygoid muscles and of the masseter and temporalis are greatly 

 expanded. AVe accordingly find that Adapis also has the malar and the 

 sagittal and lambdoidal crests highly developed, and that in the dentition 

 this superior cnishing power is shown in the expanded talonids of the 

 lower molars and in the expanded protocones of the upper molars. In 

 short, the skulls and dentitions of Adapis and NotJiarctus are funda- 

 mentally similai- in architectural plan, but differ in adaptive details. 



The limbs of Adapis are also fundamentally similar to those of Noth- 

 arctus, Adapis being more robust. It is noteworthy that the astragalus 

 of Adapis agrees with that of Notlmrdus in having a narrow vertically 

 extended trochlea, whereas in all the Anthropoidea the trochlea is wide 

 and has more distinct keels. 



I would therefore define the family Adapida^. and the included sub- 

 families Xotharctinag and Adapinoe as on page 433, below. 



Coming now to the structural relationships of the N"otharctida:> to 

 modern Primates, I can only emphasize what I liave previously stated 

 (1913), that in my judgment there is no justification for associating the 

 Notharctinffi with the South American monkeys, as AYortman (1904) has 

 done in placing both Adapis and Notliarctus, along with Tarsius, in his 

 major group Xeopithecini. The Notharctinje are certainly in a lemuroid 

 rather than a simian stage of evolution, and they differ from modern 

 Lemurs chiefiy in being more primitive and in having avoided both the 

 peculiar lemurid specialization of the lower incisors and canines and the 

 secondary elongation of the lacrymal on the face. 



The skull of NotJiarctus is lemur-like in general form. I'he face is 

 long; the postorbital bar reaches the malar; the malar is essentially 

 similar to that of Lemurs; the orbit is not shut oft' from the temporal 

 fossa by a transverse partition. But in many ways tlie skull of NotJi- 

 arctus is far more primitive than that of existing Lemurs and approaches 

 the skull of other primitive Eocene mammals; thus the brain-case is 

 relatively small and is surmounted by well-developed sagittal and lamb- 

 doidal crests; the jaw is stout: the dental formula is I-' C— ' Pj' M'-' 



which differs from the primitive Placental formula of — ' — —' ;r only 



^ 3. ]. 4. 3. "^ 



in the loss of one upper and one lower incisor. The base of the cranium 

 is fundamentally similar to that of the Lemuridos. 



The existing genus Lepilemur, which in many characters is perhaps 

 the most primitive of the Lemuridas, is far more advanced than NotJi- 

 arctus in the expansion of its brain-case, in the loss of the sagittal crest. 



