232 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



the Adapinffi and Notharctinse it seems probable that the ancestral protoadapine stock had the following 

 skull characters : 



Skull mesocephalic ; orbits guarded posteriorly by a fronto-malar bar, orbits not very large; malar 

 closely approaching or touching lacrymal; lacrymal wholly within orbit; lacrymal foramen marginal; 

 malar probably not extending back to glenoid; low sagittal and lambdoidal crests, postorbital constric- 

 tion moderate; brain-case not greatly expanded; supraorbital and interparietal not expanded to form a 

 flat occipital roof; lower jaw slender with unexpanded angle; opposite rami not fused at symphysis. 

 Middle part of cranium not shortened. Pterygoid plate of alisphenoid elongate, extending postero- 





5.AMER. 



N.AMER. 



N.ASIA 



EUROPE 



AFRICA 



MADAGASCAR 



RECENT 

 PLEISTOCENE 













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 >: -5 ^ ^ ^ 



PLIOCENE 













// < / / 



^ 1 



MIOCENE 















? /// 



/ / / 



OLIGOCENE 





^ — 











1 



1 / 



1 ,v 



EOCENE 





\ 



\ 



\ 







1 ^1 







PALEOCENE 







leTnuroc'dea 

 1. /. J. 

 i /. Y. 3. 









PROBABLE ORIGIN AND DISPERSAL 



OF THE 



LEMURIFORMS 



Fig. 82. Summary of the author's provisional conchisions regarding the origin, dispersal, and genetic relations of the 

 lemuriform primates. 



externally to contact with interoexternal process of bulla and with entoglenoid region of squamosal. 

 Auditory region as in Notharctus: ring-like tympanic enclosed within bulla; anterior end of tympanic 

 in contact with entoglenoid region, posterior end in contact with periotic, in front of carotid foramen 

 and below post- tympanic process 'of squamosal; internal carotid canal running from posteroexternal angle 

 of bulla forward on outer side of cochlea, piercing basisphenoid; stapedial branch present; bulla formed 

 as an "osseous bubble" in the periotic, smTounding the membranous cavity of the latter (sinus hypo- 

 tympanicus); communicating with the true tympanic cavity through the pneumatic foramen; osseous 

 cochlea with about two coils; fenestra rotunda concealed from external view by post-tympanic process 



