POLYGYRIDAE 43 



21. Shell 1 inch or more in diameter 22 



Shell % inch or less in diameter 23 



22. Peristome wide and pure white. . . .albolabris albolabris, p. 49* 

 Peristome narrow and pinkish in color, .albolabris alleni^ p. 49 



23. Aperture of shell contracted, three-fourths as high as wide. 



pennsylvanicay p. 55* 



Aperture of shell broad, four-fifths as high as wide, p. 51... 24 



24. Color of shell brownish or chestnut. . multiline ata rubra, p. 51 

 Color of shell yellowish or whitish. . . .multilineata alba, p. 51 



25. Peristome without denticles, p. 50 26 



Peristome with 1 or 2 denticles, pp. 47, 53 29 



26. Shell Yi inch or less in diameter; parietal denticle long and 



narrow, extending backward almost to umbilical region. . 



inflecta edentata, p. 47 



Shell approximately 1 inch in diameter; parietal denticle 

 short, not extending backward almost to umbilical region. .27 



27. Shell convex, much wider than high; parietal denticle only 



sHghtly developed albolabris dentata, p. 49 



Shell globose; parietal denticle well developed, p. 50 28 



28. Spire depressed-dome shaped; aperture large, round; parietal 



denticle, short, tubercular in shape zaleta, p. 50 



Spire elevated-dome shaped; aperture contracted, elongate; 

 parietal denticle long, curved elevata, p. 55* 



29. Periphery of shell angled or sharply keeled, pp. 52, 53; 



upper denticle on outer lip large and extending con- 

 spicuously from peristome, p. 53 30 



Periphery of shell rounded, p. 47; upper denticle on outer 

 lip small and tubercular, or wanting entirely, pp. 47, 54. .31 



30. Periphery of shell angled palliata, p. 52 



Periphery of shell sharply keeled obstricta, p. 53 



31. Denticle on parietal wall of shell not extending backward to 



umbilical callus, p. 54 32 



Denticle on parietal wall of shell extending backward to 

 umbilical callus, p. 47 ZZ 



32. Outer lower lip of shell with 1 small denticle; parietal 



denticle short, only slightly curved appressa, p. 54 



Outer lower lip of shell with 2 distinct denticles; parietal 

 denticle long, curved fosteri, p. 54 



3d>. Outer lip of shell with well-defined denticles 



inflecta inflecta, p. 47 



Outer lip of shell with denticles vague, reduced to mere 

 swellings inflecta media, p. 47 



34. Parietal denticle, viewed from front, obscuring all but a 



small opening at upper part of aperture. . . .stenotrema, p. 58* 

 Parietal denticle, viewed from front, not obscuring most of 



aperture, but leaving a part of lower lip visible 



hirsuta, p. 59 



