30 University of Michigan 



era bush form) were the most common plants of the under- 

 growth. 



Habitat 4p. Sturgeon River Flats. In places along the Stur- 

 geon and its branches are low flats, which were flooded even 

 in slight overflows. These were usually shaded by tag-alders, 

 ashes, red and white maples, arbor vitae and elms, and had a 

 sparse undergrowth of the sensitive weed, Joe-pye weed, etc., 

 with scattered but rank clumps of nettles. These flats appeared 

 to be rather unfavorable to land molluscs, probably on account 

 of the intermittent floods which covered everything with a 

 layer of fine silt. Lymnaea obrussa peninsulae was represented 

 by many living specimens crawling in the newly-drained mud. 



List of Species 



ViVIPARID/E 



Campelouia decisnm (Say). Habitats: 5, ym, 8, 10, 11, 26, 



31, 32, 34, 35. A specimen from the first locality measured: 

 alt. 30.6 mm. ; g. diam. 19.3 mm. Most abundant in river 

 invasions of Brown Lake, next in larger streams. 



VA1.VAT1D.E 



Valvata tricarinata (Say). Habitats: 4, 5, 6, 7, 8, 10, 27m, 



32, 34. ]\lost abundant on sandy marl bottoms of lake shores. 

 Valvata tricarinata confusa Walker. Habitats : 7m, 27m. 

 J^alvata tricarinata nnicarinata DeKay. 27m. 



Valvata tricarinata simplex Gould. 27m. 



Valvata sincera Say. Habitats : 4, 5, 6m, 7m , 27m. Ditto 

 preceding species. 



Valvata sincera, approaching var. nylanderi Dall. A few 

 specimens approaching this form found buried in the soft bot- 

 tom of an ash-cedar swamp (15). 



