228 



It has the power of throwing its fliell about in an extra- 

 ordinary manner, either in defence, or to remove ob- 

 flruftions, continuing at the fame time fixed by its foot. 

 Probably this fingular motion is fometimes ocrafioned by 

 a minute fpecies o^ Hirudo,* which infcRs this and many 

 other trefh-water teftaceous animals ; twenty or more may 

 ) be feen adhering to its fides like flender white filaments. 



This Leech is not uncommon on the Helix peregra, H. 

 fojfaria, and H. nautiUus ; as well as the Patella Jluviati- 

 lis ; and probably on all other animals belonging to uni- 

 valve tcjlacea at particular feafons, which inhabit frefii- 

 water. 



IS. ~ * 



Hypnorum. Bulla Hypnorum. Z//;. iyZ. p. 11S5. 



Gmd Syjl. p. 3428. 19. 



Chem Co;/c/i. ix. t.l03.f.882.8S3.a.b.c. 



Turt. Lin. iv. p. 353. 



Schroet Fhiffconch. t. 6. f.9. & f. 15. a. b. 

 Bucc. heteroflrophon. Lijier Conch, t. 1059. f. 5. 



Petiv. Gaz. t. 10. f.8. 



Favan. t. 61. F. 18. 

 Turbo JValk Min. Shells, f. 54. 



Planorbis turritus. MuUer Verm. ^. 169. No. 354. 



B. with five or fix, reverfed, taper, fmooth, glofiy, 

 pellucid, horn-coloured fpires: the body-whirl half the 

 length of the fhell, the others tapering to a fine pomt ; 

 aperture narrow at the top, fpreading a little at the bafe; 

 outer lip extremely thin ; pillar lip a little thickened : 

 * Gordius iiiquilinus. Mull. I'erm. i, p. 33. No. 164. 



Columella 



