30 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.63. 



Thus Gregory had discussed and compared the principal remaining 

 skeletal elements of Nothardus, with no hetter success in establishing 

 his hypothetical case of lemurine affinities of the group represented 

 by this genus than is indicated in the foregoing pages. 



In addition to, and perhaps of even more importance than, the 

 evidence just reviewed, there are certain modifications in tlie skull 

 and dentition of Notharctus, also discussed by Gregory and set aside 

 as of but little importance, which seem to me to preclude the possi- 

 bility of a derivation of any of the modern lemurs from the Notharc- 

 tine group. I refer here especially to the fusion of the lower jaw 

 symphysis; the modifications of the anterior teeth, which include 

 the normal development and function of the incisors and canines 

 above and below; and the form and position of the lachrymal which 

 lies within the orbital rim. These are all strictly anthropoid and 

 nonlemurine characters, as has been asserted by Wortman and others, 

 and which, moreover, can not be explained away, as Gregory has 

 attempted to do, without ignoring all known facts regarding progres- 

 sive evolution, and relying on purely hypothetical conjecture. An 

 ununited, or closely sutured lower jaw symphysis is the primitive 

 condition in mammals, and a fused symphysis, in whatever group 

 found, is always considered a specialized condition. To assume there- 

 fore that the lemurs, none of whose living representatives have a 

 lower jaw with fused symphysis, could have been derived from an 

 Eocene group in which the symphysis at that early date is either 

 fused or shows an obviously strong tendency to fusion, as in the 

 Adapidae, would be to assume a most improbable reversion of devel- 

 opment for which there is not the slightest proof. The reduced 

 lachrymal found in the Adapidae is another feature which can not be 

 considered a primitive character for the Primates, as assumed by 

 Gregory, without again resorting to a supposition of reversion in 

 evolution of characters for which there is not the slightest evidence 

 which might be taken as proof. 



As regards the peculiar modifications of the anterior teeth ob- 

 served in the true lemurs, in which the lower canines have become in- 

 cisiform, taking a procumbent position with the incisors, and in which 

 one of the premolars has become caniniform, it will again require a 

 vast amount of explaining based on pure conjecture to derive this 

 modification from such a condition as is found in Notharctus and 

 Ada pis. In these genera the lower canine is moderately large and 

 functions normally as a canine, and there is a tendency to reduction 

 rather than enlargement of the anterior premolars. 



There still remains to be discussed the two principal skull charac- 

 ters upon which Gregory has seemed to rely in defending his theory 

 for a lemuriform stage of development for Notharctus. These are 

 the presence of the postorbital bar and the modifications of the audi- 



