6 Tmns. Acad. ScL of St. Louis. 



Physa gyrina Say. 



Stony Point; Sulphur Island; Isaacson's farm; Thunder 

 Bay Island ; Thunder Bay Kiver. 



Specimens from the last locality are small and shining and 

 are very smooth for the species. Ox Bow specimens rather 

 thin. Sugar Island ; some specimens approach variety oleacea, 

 having more of a dome-shaped spire. A few specimens are 

 very like Tryon's figure of aurea in Haldeman's monograph. 

 Gyrina and its varieties may be known by their looped-shaped 

 aperture and obtuse, more or less dome-shaped spire. Close 

 attention to these two points will greatly aid in their determi- 

 nation. The surface sculpture is also very pronounced, con- 

 sisting of very strong spiral impressed lines, giving the 

 surface a wavy aspect. 



Physa gyrina oleacea Try on. 



Thunder Bay Island; Squaw Island (large and shining); 

 Thunder Bay River, Ox Bow; Sugar Island. 



Oleacea is distinguished from gyrina by having a low, 

 dome-shaped spire which forms an almost unhroJcen curved 

 line from the spire to the base of the aperture . In the writer's 

 report on the MoUusca of the Chicago Area this variety was 

 called elliptica ; the form thus designated should be called 

 oleacea, as elliptica appears to be a valid species. On plate 

 34 of that report the extreme upper left hand figure of 4 is 

 typical gyrina, while the two right hand figures of 5 are 

 typical oleacea. It is with some hesitancy that the specimens 

 under consideration are referred to oleacea . They are wider 

 than the typical oleacea (as defined by Crandall), the outer 

 lip is more convex and the sculpture is not as coarse. They 

 have several characteristics in common with aurea Lea. The 

 above disposition seems to be the best until more is known 

 concerning some of the ambiguous synonyms. 



Physa heterostropha Say. 



Thunder Bay River; Long Lake: Trowbridge's dock, 

 Alpena. 



Specimens from the first-named locality are very large, 

 with elevated spire and smooth, shining surface. A few 



