32 University of Michigan 



15.9 mm,; g. diam. lO.i mm.; alt. apert. 11.9 mm.; the next 

 largest: alt. 11.6 mm.; g. diam. 7.9 mm.; alt. apert. 9.7 mm. 



Pliysa sa\ii Tappan. Habitats : 28, 31. Two specimens only, 

 from Sturgeon River, 



Physa ancillaria Say. Very abundant at Sand Portage (35) 

 in the Menominee River. Shells rather fragile ; light and dark 

 horn-colored, with callus sometimes tinged with orange. Meas- 

 urements : alt. 15.5 mm ; g. diam. 10 mm. ; alt. apert. 12 :6 mm. ; 

 and alt. 13.2 mm.; g. diam. 8.7 mm.; alt. apert. 11.4 mm. 



Physa ancillaria vinosa Gould, Abundant just below Upper 

 Twin Falls, Menominee River (34). Shells heav}^; dark horn- 

 colored to reddish, with purplish line inside of callus. An 

 example: alt. 15.8 mm.; g. diam. 11.7 mm. ; aper. alt. 14.8 mm. 



Physa heterostropha Say. Habitat 18; a single, juvenile 

 specimen. 



Physa walkeri Crandall. Habitats : 20, 21, 22. Quite typical 

 of the brooks. The largest example, from the last habitat : 

 alt. 1 1.4 mm.; g. diam. 6.2 mm.; alt. apert. 7.9 mm. 



Aplexa hypnonim (Linn.). Habitats: 18, 19. Rather local; 

 onh' from temporary swamps. Specimens rather small ; the 

 largest: alt. 12.2 mm.; g. diam. 5.1 mm. 



Planorbid^ 



Planorbis trivohns Say. Habitats: lom, 11 , 12, 17. Mainly 

 in small lakes and permanent pools. Specimen from Hanbury 

 Lake: g. diam. 26.2 mm.; 1. diam. 22.4 mm.; alt. apert. 12.7 

 mm. ; alt. opposite apert. 10.4 mm. ; alt. inside apert. 9 :5 mm. 

 The subfossil specimen from Jackson Lake: g. diam. 27.5 mm. 



Planorbis antrosus Conrad. Habitats : 1 1 , 31 , 34. Hanbury 

 Lake specimen approaches typical form, being quite light in 

 texture and having distinct, but not extremely prominent, 

 growth lines (Xo. i). Those from the rocky habitats of the 



