NORTH AMERICAN CONCHOLOGY. 



59 



32 

 32 



Iff INFEROBRANCHIATA, not observed. 



fftt TECTIBRANCHIATA. 



Bulla oryza. 



Bulla fluviatilis. 

 insculpata. 



32 

 32 



triticea. 



ft HETEROPODA, not observed. 

 tttttf PECTINIBRANCHIATA. 



