10 Trans. Acad. Set. of St. Louis. 



variety. The lines are very distinct on young shells. Typical 

 specimens measure as follows : 



Diameter 12.00; height 6,50 mill. 

 " 11.00; " 6.00 " 



f« 12.00; " 6.50 " 



Planorbis campanulatus Say. 



Long Lake. Common and typical. 



Planorbis parvus Say. 

 Alpena. Common. 



Planorbis deflectus Say. 



Long Lake, apparently rare; Alpena, common. 



Lymnaea stagnalis appressa Say. 



Long Lake. One specimen is very long and narrow. 



Lymnaea stagnalis jugularis Say. 

 Alpena. Fairly common. 



Lymnaea palustris Miiller. 



(1) Thunder Bay Island; (2) Stony Point; (3) Sugar 

 Island; (4) Sulphur Island ; (5) Long Lake; (6) Whitefish 

 Point; (7) Isaacson's farm. 



The series of palustris, embracing several hundred speci- 

 mens, is a very interesting lot of shells, showing as it does 

 the effect of different environments. The specimens from 

 (1) are very variable with heavy, thick shell, and lip margins 

 joined by a heavy raised callus covering the parietal wall. 

 This callus is sometimes erect, as in emarginata. The spire 

 is long, sometimes scalariform, and the shell corresponds 

 closely to the form described by Say as elodes. The speci- 

 mens from this locality exhibit admirably the effect of the 

 heavy seas of Lake Huron. 



Specimens from Whitefish Point are thinner and the spire 

 is not so pointed. They are, however, subject to great dis- 

 tortion ; in many cases the entire aperture is free from the 

 body whorl and the suture is frequently channelled for quite 

 a distance on the last whorl. Some specimens are slender 



