TNIVALVE SHELLS. 4-9 



Helix pollta. — The Polished Helix. Plate II. fig. &. (Fy- 

 ramis politus, Brown.) Shell strong, white, glossy and smooth, 

 with from nine to twelve volutions, scarcely defined by a separ- 

 ating line, slender and gradually tapering to a point ; aperture 

 oval, outer lip thick, but not marginated, inner or pillar-lip repli- 

 cated. Found in Devonshire, Dorsetshire^ Northumberland, 

 and at Dunbar in Scotland. 



A Apex, B base, e e suture of the spire or whorls, c aperture. 



Helix nemoralis. — The Wood Helix. Plate III. fig. 2. 

 Shell imperforate sub-globose, thin and sub-pellucid, colour va- 

 rious ; volutions five, with from one to five dark brown bands or 

 fasciae ; aperture pyriform; inner margin of the lip sometimes 

 white, in others dark-reddish brown. This shell is very com- 

 mon in the evenings and mornings in summer, at the roots of 

 hedges, &c. 



N Outer lip, x epidermis, y epidermis removed. 



Helix glutbiosa — The Glutinous Helix. Plate III. fig. 5. 

 (Lymngea glutinosa, Lamarck). Shell suborbicular, thin, and 

 diaphanous, of a glossy, pale horn-colour, smooth, but sometimes 

 with obsolete wrinkles ; the body very large ; spire very small ; 

 volutions three ; aperture very large, extending nearly to the 

 apex. Found by Mr Montagu, in the marshes at Deal. 



G The back, h the venter, L whorl or volution. 



Helix putris.— The Ditch Helix. Plate III. fig. 10. 

 (Lymnsea ovata, Lamarck.) Shell sub-pellucid, and horn-co- 

 loured ; spire with four volutions ; the body tumid and large ; 

 wrinkled longitudinally; apex very small, fine and pointed, 

 aperture oval and large, outer-lip very thin ; outside covered with 

 a dusky epidermis, inside pale, yellow, and very glossy. 



Common in most ponds, ditches, &c. 



Helix planorhis' — The Flattened Helix. Plate III. fig. 

 14. (Planorbis carinatus, Lamarck.) Shell depressed and sub- 

 pellucid, horn-coloured, rufous, or light chestnut brown ; gene- 

 rally with a light umber-coloured epidermis ; volutions five, pla- 

 ced laterally on each other, gradually decreasing to the centre, 

 making the shell concave at top, rounded and defined by the su- 

 ture ; striated across the whorls ; a carinated ridge round the 

 margin at the base ; aperture angulated, and slanting towards 

 the base. Inhabits ponds, rivers, and ditches in Britain. 



He/u- i?<6M/ato.— The Awl Shaped Helix. Plate III. fig. 



E 



