32 



VIII. HELIX. 



Shell orbicular, thin, with a pyramidal spire which is 

 rather obtuse and consisting of five or six volu- 

 tions. Aperture lateral, semilunar or semi-eUiptic ; 

 the margin interrupted by the convexity of the 

 penultimate volution : operculum none. 



Confined to the above character, this is now a very 

 natural family, abundantly and universally spread 

 over the surface of the whole earth. And although 

 some of them, more particularly the H. Pomatia, 

 have the aperture guarded in the winter by a 

 cretaceous epithem, or by a more or less thick 

 cuticle, they cannot be said to possess a regular 

 operculum, as this covering is not attached to the 

 animal, and therefore not moveable at its control, 

 but is dissolved in the spring, leaving the aperture 

 naked. 



They feed on fruits, and animal and vegetable sub- 

 stances; are furnished with four tentacula, the 

 two front ones shorter, and all of them having eyes 

 at their tips. Many of them, in the spring of the 

 year, when they approach each other, eject or cast 

 forward a spiculum or dart ; and this with suffi- 

 cient force to strike each other : this dart is gene- 



