178 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



Opalina ohtrigonoidea and its subspecies have a wide distribution 

 from the whole Atlantic coast of North America to Alaska and Cen- 

 tral America. It is likely that breeding experiments, if possible to 



i 



Fio. 143. — Opalina obtkigonidea, from Bufo fowlbri, x 117 diametbes. 



carry out, would elevate to specific rank some of the forms here 

 treated as subspecies, but their structure alone is not sufficient to 

 demarcate them as species. The species ohtrigonoidea is differen- 

 tiated from 0. ohtrigona by its greater diversity in form, not only 

 between different infections, but between different individuals in a 



