LYMN^EHXE OF NORTH AMERICA. 315 



the American shells. It may be noted in passing, that until some Euro- 

 pean author revises the nomenclature of the European varieties and 

 so called species it will be absolutely impossible to make any intellig- 

 ible comparisons. The tendency of some of the students of fresh- 

 water shells is to make every mutation a species or variety. A similar 

 course practiced on our American palustris would produce several 

 hundred of these "species." 



Galba palustris alpenensis Nov. Var. Plate XXXIII, figures 

 26-33. 



Lymncea palustris BAKER, Trans. Acad. Sci. St. Louis, XVI, p. 10, 1906. 

 (part). 



Lymncea palustris michiganensis BAKER, Trans. St. Louis Acad. Sci., XVI, 

 p. 12, 1906. 



SHELL: Elongated, narrow, very solid; periostracum light horn- 

 colored; sculpture as in palustris; whorls six to seven, well rounded, 

 the body whorl somewhat obese ; spire long and acutely conical, usually 

 considerably longer than the aperture ; sutures well impressed ; aper- 

 ture regularly oval; outer lip thickened internally by a well marked 

 varix; inner lip rather wide, reflected over the umbilical region, either 

 completely closing the perforation or else leaving a very small chink; 

 the parietal callus heavy, producing a continuous aperture in many 

 specimens ; there is in some specimens a more or less distinctly marked 

 plait, but the majority of specimens are without a distinct columellar 

 plait, though the axis is distinctly twisted. 



Length. Breadth. Aperture length. Breadth. 



24.25 10.50 11.00 5.50 mill. Type 



23.00 10.00 10.50 5.25 " " 



22.00 10.00 10.00 5.00 " " 



19.75 9.00 9.50 4.00 " 



21.00 10.00 10.50 5.00 " 



16.25 8.00 9.00 4.50 " " 



TYPES : Chicago Academy of Sciences, eight specimens, No. 23486. 

 TYPE LOCALITY : Thunder Bay Island, near Alpena, Alpena Co., 

 Michigan. 



ANIMAL, JAW, RADULA and GENITALIA: Unknown. 

 RANGE : Michigan. A race of the Canadian region. 



RECORDS. 



MICHIGAN: Thunder Bay Island; Long Lake; Whitefish Point; Sugar 

 Island, all near Alpena, Alpena Co. (Nason). 



GEOLOGICAL DISTRIBUTION: Unknown. 



ECOLOGY: This race lives on an exposed shore in pools on lime- 

 stone ledges where the waters of Lake Huron dash in, producing a 



