48 HELIX. SNJIL-SHELL. 



of the flattened surface of the outer volution, ami some- 

 times produced into an oblique angle at the upper and 

 outer end, the margin thin, and slightly embracing the next 

 volution at the sides : diameter the tenth of an inch. 



This new species, sufficiently distinct from any of its di- 

 vision by the mouth, which forms an oblique parallelo- 

 gram, resembles the H. albina of Gmelin, except that it is 

 nearly equally concave on both sides : we have as yet only 

 found it, attached to the cases of the Phryganeae, in its InrVa 

 state, in the pond at Glasnevin botanic garden, near Dublin, 

 where they are met within tolerable abundance. These cases 

 are chiefly clothed with this shell, the H. planorbis and 

 planata ; Turbo fontinaiis, and the young of Tellina cor- 

 nea, v. v. 



9. Helix contorta. Coiled Snail-shell. 



Montagu, pi. 25. f. 6-~Da Costa, pi. 4. f. 11 Donovan, 

 pi. 99 Dorset Cat. pi. 20. f. 11. 



Shell fiat, horn-color, sometimes rufous or whitish, con- 

 cave in the very centre only on one side, but largely and 

 deeply so on the other : spires six, rounded, finely striatc, 

 deeply divided by the line of separation : aperture narrow 

 crescent-shaped, like the moon in its first quarter, painted 

 at the sides : diameter hardly two tenths of an inch. 



It differs from H. spirorbis, in the deep cavity on one 

 side, the narrow aperture, and the number and compactness 

 of the volutions. 



Ponds and wet ditches, v. v. 



10. Helix alba. White Snail-sheU. . 



Montagu, pi. 25. f. 7 Dorset Cat. pi. 19. f. 18 [Patten, 

 f. 19. 



Shell flattish, pale horn-color, semitransparent, often co- 

 vered with a brown skin, slightly concave on. one side &nd 

 more deeply so on the other : spires four, finely rounded, 

 very closely but distinctly striate both across and Circu- 

 larly j the larger volution very faintly inclining to an edge 

 or keel : aperture somewhat orbicular or crescent-shaped, 

 a little oblique and clasping the spire : diameter a quarter 

 of an inch. 



Ponds and slow streams, v. v. 



11. Helix 



* :--V\ 



