UNIVALVES. — HELIX. 125 



Division X. — Shell depressed. 



*Nautileus — Nautilus, *Serpuloides — Serpula. 



*Cristatus — Small-crested, Ludus — Green-spotted. 



*Depressus — Minute-flattish. Marginellus — Reflected- lip. 



HELIX. — Snail or Spiral. 



Animal — a Liniax : Shell univalve, spiral, subdiaphanous, 



brittle; aperture contracted, semilunar, or roundish. 



THE one hundred and ninety-four species, which com- 

 pose this genus, are principally land or fresh water shells, 

 a few only being the produce of the ocean. They are 

 usually of a delicate and brittle structure, and remarkable 

 for their lightness; their general form resembles that of 

 the common garden or hedge-snail, except in those species 

 which are tapering or elongated. 



The first division consists of the carinated Helices, and 

 the more compressed or flattened species of the genus; 

 which, from their shape, are commonly called Antique 

 Lamps. The H. lapicida, H. marginata, and H. cicatri- 

 cosa, have acute margins, and are characteristic of the ca- 

 rinated species. These shells were formerly supposed to 

 have fallen in showers from the clouds. 



Of the Antique Lamps, the H. lucerna, H. lampas, and 

 H. carocolla, are illustrative specimens. The rarest spe- 

 cies are the H. ringens, H. Gualteriana, and H. otis. 



Some of the species of the third division are umbilicat- 

 ed, and are much more globose or inflated in their forms, 

 as the H. pomatia; which snail is an inhabitant of the 

 woods of Europe, and was introduced into England by Sir 

 Kenelm Digby, for medical purposes. The animal is used 



