120 THE NAUTILUS. 



Punctum pyc/mczum (Drap.). Thief River Falls. 



Succinea retusa Lea. White Earth Lake, var. Thief River Falls. 



Succinea ovalis Say. Thief River Falls, var. Minneapolis. 



Succinea avara Say. Thief River Falls, Cannon Lake. 



Succinea avara vermeta Say. White Earth Lake. 



Strobilops virgo (Pils.). Thief River Falls. White Earth Lake. 



Bifidaria contracta (Say). Thief River Falls, White Earth Lake. 



Bifidaria pentodon (Say). Thief River Falls. 



Bifidaria tappaniana (C. B. Adams). White Earth Lake. 



Bifidaria holzingeri Sterki. White Earth Lake. 



Cochlicopa lubrica (Miiller). Thief River Falls. Also a form 

 which seems to be G. 1. morseana Doherty. 



Vallonia cosfata (Miiller). Thief River Falls, White Earth Lake. 



Carychium exile canadense Clapp. Thief River Falls, White 

 Earth Lake. 



Lampsilis luteola Lam. Thief River Falls. 



Anodonta kennicotti Lea. Thief River Falls. 



Unio gibbosus Barnes. Thief River Falls. 



Quadrula lachrymosa Lea. Thief River Falls. 



Spl cerium simile Say. Lake Harriett. 



Sphcerium occidentals Prime. Thief River Falls. 



Musculium jayanum Prime. Thief River Falls. 



Pisidium sp. Thief River Falls. 



Gampeloma subsolidum Anthony. Mississippi River, Minneapolis. 



Cantpeluma rufum Hald. Lake Harriett. 



Gampeloma milesii Lea. Thief River Falls. 



Valcata sincera daniehi Walker. Cannon Lake. 



Valvata tricarinata Say. Cannon Lake. 



Valvata tricarinata simplex GUI. Cannon Lake. 



Amnicola limosa Say. Var. Cannon Lake. 



Pliysa ancillaria Say. Lake Harriett. 



Physa yyrina Say. Lake Harriett. 



Pliysa gyrina liildrethiana Lea. Thief River Falls. 



Physa qyriiia oleacea Tryon. White Earth Lake. 



Aplexa liypnorutn (Linn.). Thief River Falls, Halma. 



Lymnaa stagnolis appressa Say. Thief River Falls, White Earth 

 Lake, Halma, Lake Harriett. 



Lymi/cen stagnalis var. Lake Harriett. 



Lymnaa obrussa Say. Thief River Falls, Cannon Lake. 



