Explanation of Plate. 



Fig. 13. — Shows tracings of mesial sections of an aboriginal Australian skull (above) 

 and a modern European skull (below), in order to demonstrate how much 

 the spheno-maxillary angle has become reduced in size in order to produce 

 the orthognathous type of skull. In the Australian skull this angle was 

 found to be 93°, and in the modern European type 76°, the former thus 

 representing a half way stage, so far as this angle was concerned, between 

 the anthropoids and the white races of modern mankind. Note that both 

 limbs of the angle have been affected, and that the anterior limb shows a 

 further swing backwards of the pendulum (see Fig. 12). The spheno- 

 ethmoidal angle is indicated by N Pr. B. Note how it also becomes re- 

 duced in size in the white races. 



