12 Trans. Acad. Sci. of St. Louis. 



Length 32.00; width 12.50 mill. 

 " 28.60; " 12.00 " 

 " 30.00; " 13.00 " 

 " 25.00; " 13.00 " 

 " 17.00; " 8.50 " 



Lymnaea PALU8TRIS MiCHiGANENsis Walker. 

 Stony Point; Thunder Bay. 

 Small, but typical; associated with palustris. 



Lymnaea emarginata Say. 



Squaw Island. Apparently rare. 



Lymnaea Catascopium Say. 



Fl. I, Jigs. 13, 14, 15, 16. 



Trowbridge dock, Alpena. 



Several juvenile specimens seem referable to this species, 

 although differing in some respects, and several are figured 

 for future reference. 



Lymnaea nasoni n. sp. 



PL I, Jigs. 1,2, 3,4. 



Shell rather small, roundly inflated, solid; whorls four, 

 rounded, inflated, last whorl very large and bulbous ; color 

 whitish, tinged with purple; surface dull, marked by rather 

 coarse growth lines crossed by fine impressed spiral lines ; 

 apex small, rounded, smooth, dark brown in color; spire 

 very short, depressed, one-third the length of the shell; 

 sutures well impressed; aperture broadly ovate, almost round 

 in some specimens; outer lip somewhat expanded, thickened 

 internally by a callus ; columella with the plait and twist of 

 catascopium; the columellar callus is rather heavy in the 

 columella region but thin where it covers the parietal wall; a 

 small umbilical chink is present. 



Length 10.00 

 " 10.50 

 " 9.50 



8.50 



width 6.75; aperture length 7.00; width 5.00 mill. 

 " 6.75; " " 7.00; " 4.25 " 



" 6.00; " " 7.00; " 5.00 " 



" 6.00; " " 6.25; " 4.00 " 



Habitat: — Thunder Bay Island. 



Nasoni was at first thought to be a variety of catascopium 

 but it seems distinct enough to be accorded specific rank. 



