238 BULLETIN 114, UNITED STATES NATIONAL MUSEUM. 



ticular of any two adjacent forms, but, as the differences registered 

 in the pattern are more evident and more distinctive than any others, 

 these have been made the main basis of distinction between differ- 

 ent forms. However, near the bomidaries between any two ranges 



Fig. 63.— Map showing distribution of the various forms of the Triangulum group. 



even these distinctions break down and we find individuals which 

 can not be definitely assigned to either form. This completes the 

 proof furnished by the structural features of the close relationship 

 existing between all these forms. 



