106 UNIVALVES. 



V 



dye differs in many respects from that obtained 

 from the Buccinum Lapillus. It can be pro- 

 duced spontaneously from the mollusca ; the 

 colour when first discharged from the animal is 

 purple, and not of the same unalterable nature 

 as that obtained from the other shell. 



GENUS^-HELIX.* 



SNAIL. 



f Generic character. Shell univalve, spirally 

 convoluted, sub-diaphanous,")* thin and fragile ; 

 aperture entire, contracted, sub-orbicular ; body 

 whorl generally projects into the mouth, sepa- 

 rating the lips. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The shape of the Helix varies considerably : 

 some of the species exhibit quite a turreted 

 form ;J in others the whorls are arranged on a 

 horizontal plane, so that the spire is quite flat- 

 tened, and the course of the volutions may be 



* Plate V. figures 1, 2, 3. 



f Diaphanous is from the Greek words &a, (dia) through, and 

 <f>aivta, I appear. 



I Plate V. figure 3 



II Plate V. figure 2. 



