50 LINNEAN GENERA. 



7. (Pyramis subulatus, Brown.) Shell tapering and subulate, 

 very smooth^ and glossy; whorls about ten, and scarcely defined; 

 colour white, with two pale-chestnut spiral lines running from 

 the body to the apex, becomin-g very faint on the upper whorls ; 

 aperture ovate, and rather contracted. Length three quarters of 

 an inch. Inhabits the sea at Weymouth and the Frith of Forth. 



D Spire, F body, o pillar-lip. 



Habitation. The Helices are found in the ocean, in lakes, rivers, and on the 

 land. They are inhabitants ot almost all countries of the globe, and are in 

 general very numerous. On land they are found to inhabit trees, old wails, 

 mossy banks, rocks ; and are often found under stones. 



The animals of this genus are termed snails in Britain ; they feed on vege- 

 tables. It has been asserted, and on apparently good authority, that sna'ls 

 have been known to revive after remaining in torpidity for a number of 

 years ; snails are possessed of very considerable reproductive powers, and 

 are capable of regenerating the head after it is taken off. 



Genus 30.— NERITA. 



Animal a Limax ; shell univalve, spiral, gibbous, flattish at 

 bottom ; aperture semi-orbicular, or semilunar ; pillar lip trans- 

 versely truncate, flattish. 



This genus is divided into three families : *umbilicate ; **imporf orate, 

 with the lips toothless ; ***im perforate, with the lips toothed. 



Ncrita Uttoralis. — The Shore Nerita. Plate IX. fig. 30. 

 (Neritoides littoralis. Brown.) Globular, thick, smooth ; spire 

 flat ; yellow, covered with an olive epidermis, beneath which the 

 shell is either yellow, orange or red, frequently with elegant zig- 

 zag lines of red, or brown. Three- fourths of an inch long. In- 

 habits the British coasts. 



The Neritae inhabit the sea, lakes, and rivers. The marine species are 

 found near the shore, and several are attached to ma-rine plants ; and some 

 are only found in deep water, so that live specimens can only be had by 

 trawling for them. 



Genus 31.— HA LI OTIS, 



Animal a Limax; shell ear-shaped; univalve and dilated, 

 with a longitudinal row of oriflces along the surface ; spire la- 

 teral, and nearly concealed. 



The animals composing the shells of the genus Haliotis, inhabit the sea 

 only. They adhere closely to rocks, and can only be removed by suddenly 

 snatching them from their hold. In some places the animal is esteemed 

 good eating. One species, the Haliotis tuberculata, is very common in 

 Guernsey, and sold in the market as food. 



