Marsh Collection, Peabody Museum. 



169 



in the 0]d World monkeys and the Anthropoids it has practi- 

 cally the same position as in the human species. In the 

 extinct Eocene apes, as far as known, the main canal pierces 

 the bulla in its posterior external portions. It should be here 

 noted, also, that the relative size of the canal steadily increases 

 from the small-brained to the large-brained forms, and that 



103 



Figuee 103. — Basal view of the skull of 'Tarsius spectrum; enlarged. 



apf, anterior palatine foramen ; if, infraorbital foramen ; ppf, posterior pala- 

 tine foramen ; mf, malar foramen ; ec, eustachian canal ; fo, foramen ovale ; 

 cc, carotid canal ; pgf, postglenoid foramen ; earn, external auditory meatus ; 

 smf, stylomastoid foramen ; vc, venous canals ; ftp, foramen lacerum pos- 

 ticum ; cf, condyloid foramen. 



this increase is directly proportioned to the degree of develop- 

 ment of the cerebral hemispheres. 



There yet remain to be described other characters of the 

 blood supply to the brain through the vertebral arteries, in 

 certain groups of the Primates, which are of importance from 

 the standpoint of classification. In the lemurs,* the New 

 World, and a few of the Old World monkeys, the course of 

 the artery through the transverse process of the atlas is some- 

 what different from that seen in Tarsius, the anthropoid 

 apes, and man. If the atlas of an anthropoid ape or man is 

 viewed from behind, the large vertebrarterial canal will be 



*The only exception which I have been able to find in this group is 

 Perodicticus potto, in which the anterior bony bridge is not quite complete. 



