289 



deep (depth to level of under side of poistglenoid process con- 

 siderably more than distance from tip of postorbital process to 

 middle of intei-parietal) but not unusually wide (mastoid breadtli 

 slightly exceeding depth to under side of postglenoid process). 

 Dorsal profile usually with an evident concavity in interorbital 

 region, but this character showing much variation ; highest point 

 at bregma or slightly further forward, the profile nearly straight 

 and sloping away at an angle of about 20° behind tliis j^oint to 

 slightly overhanging lambdal region ; ventral profile faintly and 



Fig. 51. 

 Uistis arcton. x J. 



evenly concave throughout. Brain-case broadly ovate in outline, its 

 greatest breadth about equal to distance from bregma to lambda," 

 its depth at middle, exclusive of sagittal crest, slightly less than 

 greatest breadth ; lambdoid and sagittal crests well developed in 

 adults, tlie lambda noticeably projecting so that occiptal condyles 

 are scarcely visible when skull is viewed from above, and region 

 between crest and foramen magnum is deeply concave ; sagittal 

 crest dividing in region of bregma into two ridges, one of which 



* Except in very old individuals in which the lambda is greatly 

 produced backward. 



U 



