LYMK^EID^E 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- 

 coiored; 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. 



Breadth. Aperture length. Breadth. 



11.00 5.50 mill. Type 



10.50 5.25 " 



10.00 5.00 " 



9.50 4.00 " 



10.50 5.00 " 



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 



Length. 



Breadt 



24.25 



10.50 



23.00 



10.00 



22.00 



10.00 



19.75 



9.00 



21.00 



10.00 



16.25 



8.00 



