43G THE CHICAGO ACADEMY OF SCIENCES. 



Ecology: "This form is abundant in Washington Harbor, and 

 with Limncra stagnalis constitutes the characteristic molluscan life of 

 this station. The specimens collected were found clinging to the rocks 

 under the same conditions as L. stagnalis. It was also found to occur 

 commonly in the rock pools on the Minong Trap promontory (Adams; 

 Ruthven ). 



Remarks: Pilsbryana differs from emarginata (as herein under- 

 stood) by its less rotund shape and particularly by the entire absence 

 of the inner lip emargination. It is. however, very closely allied to the 

 conical race known as canadensis, differing, as indicated by Walker, by 

 its darker color and more inflated spire whorls. The Isle Royale 

 emarginata appear to be transitional forms between typical emarginata 

 and the race canadensis, many specimens have a spire quite as wide as 

 either emarginata or pilsbryana, while others have the sharp conical 

 spire of canadensis. The characteristic of the inner lip will immed- 

 iately distinguish pilsbryana from all related species. 



Galba montana (Elrod;. Plate XLVI, figures 5-8. 



Limneea emarginata var. montana Elrod, Nautilus. XV, p. Ill, 1901 ; Trans. 

 Amer. Micr. Soc, XXII, p. 76, 1901; Bull. Univ. Mont, Biol. Ser., Xo. 3, pp. 

 112, 173, 1902. 



Limncea emarginata montana Keep, West Amer. Sh., p. 314, 1904. 



Shell : Rather large, elongated, thin ; periostracum light brown- 

 ish horn or pearl gray; surface shining; sculpture of heavy growth 

 lines crossed by heavy impressed spiral lines, giving the shell a beauti- 

 fully latticed appearance; rarely malleated; whorls 0^2 to 6, well 

 rounded, rather obliquely coiled, body whorl obese ; spire long, acutely 

 pyramidal, a trifle longer than the aperture ; nuclear whorls as in 

 emarginata; sutures well impressed; aperture roundly ovate or elon- 

 gate ovate ; interior of aperture chocolate colored ; peristome thin with 

 a slight thickening within; inner lip reflected and forming a broad, 

 fiat expansion which emargins the large umbilical chink; parietal callus 

 not generally notably heavy ; columella thickened but not plicate ; axis 

 slightly twisted 



Length. 



Width. 



Aperture length. 



Width. 





27.00 



13.25 



i 



10.25 mill. 



(Elrod.) 



29.50 



14.25 



14.50 



8.50 " 



Mission Mountains. 



28.50 





13.00 



S.00 " 



" 



31.00 



15.00 



14.00 



8.75 " 



" " 



24.50 



14.00 



12.50 



9.00 '■' 



" " 



Types : 



Collect 



ion Morton Elr 



sd. Univei 



■sitv of Montana ; t 



types. The Chicago Academy of Sciences, four specimens, Xo. 23709. 



