Fig. 52. Evolution of the 

 Bones Behind the Jaws. 



Same series as in Fig. 49. Figures 

 48-52 give excellent examples of " Wil- 

 liston's law" of the progressive elimi- 

 nation of skull elements in passing 

 from fish to man. 



~'~W'Vmr^_ 



Vll 



For details, see pp. xxiii, xxiv. 



