THE PRIMATES EXCEPT MAN 107 



the ages with the lines of specialization of other families. It 

 is usual to consider Man as the topmost twig of the phylo- 

 genetic tree while other twigs on lower planes and perhaps 

 further removed from the trunk represent other members of the 

 Primate stock. Yet it is perhaps not quite exact to speak of 

 Man as at the top unless one understand thereby a relatively 

 steady evolution in Man's history with the maintenance of a 

 still largely generalized structure even at the present day. 



Except for certain fossil representatives occurring before 

 the Primate line of evolution was thoroughly established all 

 members of the order are readily distinguishable, though details 

 of the distinctive features lie beyond the compass of this work. 

 It may be mentioned in passing that Avith the exception of cer- 

 tain Lemurs, all Primates present two upper and two lower 

 incisors and further that the orbit possesses at least a com- 

 plete ring of bone separating it from the temporal fossa. The 

 dental formula is very generally: 



I ■§, C \, P | (or P | ) , M |. total 36 ( or 32). 



Within the order are to be found, originating from a central 

 insectivorous-omnivorous type not unlike that of the Tree 

 Shrews, several forms of dentition adapted for frugivorous or 

 for herbivorous diet or even for the extreme gnawing habit. 

 Though many species will and do eat flesh, none is entirely 

 carnivorous. It is not along the purely flesh-eating line but 

 in the herbivorous direction that we find evolution of the Pri- 

 mate dentition. The general principles of this adaptation have 

 already been set forth in the chapter on Marsupials so that 

 the student may be expected to be familiar with them. It will 

 thus be an easy matter to note the increasing specialization of 

 each family discussed. 



It is not possible to utilize modern Primates to illustrate 

 progressive evolution so readily as it was in the case of the 

 Marsupials, for the order Primates does not contain among 

 its existing representatives so comprehensive a series of tooth 



