TENTATIVE PHYLOGENY OF THE PRINCIPAL SKULL TYPES 



In the preceding sections the relationships of the group in question have been dis- 

 cussed and in this way the probable steps by which each particular skull type has arisen 

 have been at least implicitly noted. The whole field, so far as I can interpret the data, is 

 summarized in the subjoined diagram (PI. II). 



The groups omitted from this diagram are either incerta sedis or have not been available 

 for the present study. 



411 



