174 THE ROYAL SOCIETY OF CANADA 



attachment or even some defect of the geniohyoglossus muscles. 

 Smith Woodward^ has, however, pointed out that Piltdown man who 

 was a chinless individual probably had these muscles well developed. 

 It would appear then that the growth and evolution or rather devolu- 

 tion of the teeth provide us with the most convincing evidence at 

 present regarding the exact way in which the chin has been evolved. 

 The effect which a well developed and shapely chin has upon the 

 general configuration, the expression and the character of the human 

 face is of course admitted on all sides. 



Q-; (-Q 



Fig. 11. — Shows a modern dental arch from the lower jaw superimposed upon the 

 Piltdown dental arcade (shown dotted). It was first of all found that the 

 average modern dental arch had to be slightly magnified so as to get any 

 of the teeth to coincide. It was then ascertained that the second molars 

 were the only ones that would thus coincide. The second molars thus 

 appear to represent the fixed points from which the alteration in the curve 

 of the dental arch has proceeded. The direction of displacement of the 

 teeth in order to form the modern dental arch is indicated by the arrows. 



It is interesting and also instructive to compare the lower dental 

 arch of a modern European type of cranium with that of the Piltdown 

 jaw. Fig. 11 has been devised for the purpose of representing this 

 comparison in a more vivid manner. It will be noted that the dental 

 arch of modern white races forms a parabola-like curve while the 

 Piltdown specimen, shown in dotted outline, forms a curve which is 

 decidedly U shaped, the latter being likewise the type of arch met with 

 in the lowest races of modern hominidse — for example the aboriginal 



1 op. cit. 



