5Q LINN^AN GENERA. 



Plate III. fig. 13. B Reversed or heterostrophe spire, a fceeth of a 

 univalve. 



The shells of this genus inhabit the sea, land, and fresh water ; they 

 adhere to rocks near the shore ; and some of them live in very deep 

 water. 



The Tm-bo scalaris, or wentletrap, is very much esteemed by collec- 

 tors, and is rather a scarce shell. 



Genus 29— HELIX. 



Animal a Limax; shell univalve, spiral, subdiaphanous, 

 brittle ; aperture contracted, semilunar or roundish. 



Linnaeus divides the Helices or Snails into six families: *angulated 

 on both sides ; **whorls with a carinate acute margin ; ***whorls 

 rounded and umbilicated; ****rounded and imperforate; *****taper- 

 ing ; ***#**ovate and imperforate. 



Helix arbustorum. — The Grove Helix. Plate IX. fig. 

 29. Sub-globose, sub-pellucid, with five volutions; mottled 

 with ash-colour, and streaked with deep chestnut zigzag 

 lines ; a single deep brown band commences at the edge of 

 the outer lip, and continues rouiui the middle of the body 

 and the volutions to the apex; |ths of an inch in diameter. 

 Inhabits groves, thickets, hedge-banks, and places covered 

 with strong herbage, in Britain. 



Helix vivipara — The Viviparous Helix. Plate 11. 

 fig. 8. (Paludina vivipara, Lamarck.) Shell with six 

 ventricose whorls, separated by a deep depressed line ; sub- 

 ovate and obtuse; of an olive green, with generally three 

 fasciae or bands on the body of the shell, and two on the 

 superior volutions, which become obscure in the fourth; 

 slightly wrinkled transversely; aperture suborbicular ; pil- 

 lar-lip reflected; sub-umbilicated. Found in the Thames 

 and New River. 



A Apex, B base, l a whorl, r r oands or fasciae. 



Helix polifa. — The Polished Helix. Plate II. fig. 9. 

 (Pyramis politus, Brown.) Shell strong, white, glossy 

 and smooth, with from nine to twelve volutions, scarcely 

 defined by a separating line, slender and gradually tapering 

 to a point ; aperture oval, outer lip thick, but not margin- 



