112 



LAND AND FRESH-WATER SHELLS OF N. A. [PART L 



the penultimate whirl, and approaching in character to, but less 

 strongly developed, than that in H. monodon. The outer edge 

 of this fulcrum is uneven — in one specimen somewhat den- 

 ticulated. 



Subgenus POLYGYRELLA, Bland. 



Shell widely umbilicated, discoidal, ribbed above, smoother 

 below ; whirls "1-8, gradually increasing, the last deflected above, 

 furnished within with two' rows of three teeth ; base flattened, 

 umbilicus of equal size to the apex ; aperture subvertical, 

 oblique, lunate-oval ; peristome white, simple, much thickened 

 within, margins joined by a white, pliciform, elevated, triangular 

 tooth. 



Helix polygyrella, Bland. — Shell widely umbilicate, discoidal, 

 flat, shining, translucent, yellowish horn-colored, ribbed above, the ribs 

 obsolete near the aperture, base rather smooth ; spire scarcely elevated ; 

 whirls seven to eight, somewhat convex, gradually increasing, 

 the last slightly dellexed above, armed within with two rows 

 of three teeth, seen through the outer wall ; umbilicus per- 

 vious, of equal size to the apex ; aperture subvertical, oblique, 

 lunate-oval ; peristome depressed above, white, simple, much 

 thickened within, the margins joined by a white, pliciform 

 elevated, triangular tooth. Greater diam. 11.}, lesser lOJ; 

 height 5 mill. 



Helix polygyrella, Bland & Cooper, Ann. N. Y. Lye. VII, 

 365, pi. iv, f. 13-15 (1861). 

 Polycjyra polygyrella, Teton, Am. Journ. Conch. Ill, 160, pi. xi, f. 26 

 (1867). 



Common on the Cceur d'Alene Mountains, especially on their 

 eastern slope, in spruce forests. 



Fig. 188. 



Subgenus STENOTREMA, Raf. 



Shell with the perforation covered, lenticular or globosely 

 depressed, hairy; whirls 4^-6, the last anteriorly gibbous, 



