^4 University of Michigan 



Flanorbis catnf)anitlatus Szy. Habitat: ii. One measured : 

 g. diam. 12.6 mm.; lesser diam. 9.8 mm.; alt. apert. 5.2 mm.; 

 alt. opposite apert. 5.4 mm. This specimen was distinctly mal- 

 leated; all of the specimens from this habitat w-^re dead, per- 

 haps killed by sewage. 



Planorbis campanulatus minor Dunker. Habitats : 5> 7 > 

 Brown Lake. A typical example measured : g. diam. 8.8 mm. ; 

 1. diam. 6.6 mm. ; alt. apert. 4.1 mm. ; alt. opposite apert. 3.8 mm. 

 Planorbis campanulatus riidentis Dall. Habitats : 4, 5, 7, 8, 

 lom, 27m. Most of the shells from Brown Lake approached 

 this form. Distinguished by the peculiar shape of the aperture, 

 which faced more directly forward and was indented along 

 the outer i)ortion of the lower side, and by the closely wrapped 

 coils, which had a tendency to be elevated near the center of 

 the shell. An example: g. diam. 13.5 mm.; 1. diam. 10.6 mm.; 

 alt. apert. 6.4 mm. ; alt. opposite apert. 6.4 mm. 



Planorbis exaciwiis Say. Habitats: 3, 5, 7m, 18. Most 

 abundant in pools and swampy shore of lake. A specimen 

 from temporary swamp (18): g. diam. 7 mm.; 1. diam. 5.9 

 mm.; alt. apert. 1.9 mm. 



Planorbis parvus Say. Habitats: 2, 6m, 7m, 8, 13, 18, 19, 

 27, 20, 21, 22. Widely distributed. 



Planorbis deUectus Say. Habitats: 4, 5, 6m, 7, 8, 27m. 

 Mainly in Brown Lake. 



Planorbis umbilicatellus Cockerell. Habitats: 2, 4, 5, 8, 12. 

 Less numerous than preceding species. 



Planorbula annigera (Say). Habitats: 15, 17. In small 

 pools. 



Lymncea stagnalis appressa Say. Habitats: 5, 6, it, 12, 



Lakes and large pool ; example : alt. 48 mm. ; g. diam. 22.8 mm. 



Lymnaa nicgasoma Say. A single dead specimen found on 



