127 

 CHAPTER XXXII. 



OF THE HELIX. GENUS XXIX. 



H E LI X. 



"Animal a Limax. Shell univalve, spiral, somewhat transparent, brittle ; 

 aperture contracted, within half-moon-shaped or nearly round, with a 

 circular segment taken away." — Linn. 



The form of the aperture in this genus is so various, that the 

 essential cliaracter can scarcely be taken from this part ; the 

 mouth is whole, or without a holloAV on the margin like the two 

 preceding- genera. The texture of the shells in almost all the 

 species is seniitransparent, which seems often to be the princi- 

 pal difference between the Trochus and Helix : many species 

 have a lunated or somewhat crescent-shaped aperture, the 

 inner lip being formed by the rounded exterior of the preceding 

 whorl, as in H. iiemoralis, aibustorum, &c. : others are nearly 

 round, having but a small portion taken out of the circle by 

 the preceding whorl, as H. corneii^ QpL 8. /. 11 5), &c. : in 

 many species of the second division, Carmat(e, the aperture 

 is nearly oval, with acute ends, as in H. complanata, Vortex, 

 &c. ; some are angulated, like the Trochus, as H. Carocolla, 

 Gualteriana (/. 1 1 6), &c. ; a great many are oval, or rounded, 

 but extended more or less into an angle tow^ard the spire, as 

 H. tentaculata, solida, piitris, stagtmlis (/. 109), &c. : the aper- 

 ture in many of these is of the same form as that of many of the 



