HELIX. 



157 



tricuspid, median cusp long and slender; laterals same shape, 

 but bicuspid ; unciui wide, short, serrated. 



ScBGE.vtTs VALLONIA, Risso. 



Shell umbilicated, depressed, diaphanous, whirls 3^-4 ; aper- 

 ture oblique, subcircular ; peristome white, thickened, reflected, 

 its margins contiguous or converging. 



Helis pulcliella, Mcll. — Shell widely umLilicated, depressed, 

 slightly convex above, thin and transparent ; epidermis colorless ; whirls 

 four, very minutely striated, the last large, and spread- 

 ing at the aperture like a trumpet ; aperture orbicular, 

 a little dilated ; peristome much thickened, white, 

 reflected, making nearly a continuous circle, ends 

 approaching ; umbilicus large, exhibiting all the volu- 

 tions. Greater diam. 3, lesser 2^ ; height Ih mill. 

 Helix pnlchella, Muller, Verm. 30. — Pfeiffer, Mon. 

 Hel. Viv. I, 365.— BixxEY, Bost. Journ. Nat. Hist. 

 Ill, 375, pi. ix, f. 2 (1840) ; Terr. Moll. 11, 175, 

 pi. xvii, f. 1.— Leidy, T. M. U. S. I, 25(j, pi. ix, f. 

 7-9 (1851), anat. — Gould, Invnrtebrata, 176, f. 

 102 (1841). — Adams, Vermont iMollusca, 159 

 (1842). 

 Helix minuta, Sat, Joum. Phila. Acad. I, 123 (1817) ; Nich. Encycl. ed. 

 3 (1819) ; Binney's ed. 3.— DeKay, N. Y. Moll. 40, pi. iii, f. 33 

 (184.3).— Morse, Amer. Nat. I, 544, f. 39 (1867). 

 Helix costata, Muller, vid. Pfeiffer, Mon. Hel. Viv. I, 366. 

 VaUonia minuta, Morse, Journ. Portl. Soc. I, 21, f. 54-56, pi. viii, f. 57 

 (1864).— Tryon, Am. Journ. Conch. Ill, 36, pi. vii, f. 26 (1867). 



From Canada East to Nebraska and Florida. Also throughout 

 Europe, Siberia, Thibet, Madeira, Azores, &c. 



The strongly ribbed variety {H. costata) has been found in 

 large numbers in Kansas, and at Cin- 

 cinnati and Philadelphia. ^^S- 271. 



Jaw long, narrow, slightly bent at 

 the ends, straight in the centre, of 

 uniform width throughout; ends j^,, of MeUx puichdia. [Morse.i 



IJeli.v palchella, 

 enlarged. 



