234 LIMNuEAD^. 



mantle a blood-red fluid similar to that of Aplysia in 

 appearance. 



Shell an inch in diameter, thick, black, or of a 

 rusty brown colour, obliquely striate ; volutions five, 

 the outer one rounded with a deep umbilicus on the 

 under or front side, exposing three of the volutions ; 

 upper surface a little concave and whitish ; aperture 

 rather oblique, rounded, as high as broad. 



b. Shell concave above; ichorls crested or ciliated; 

 mouth roundish. (Gyraulus.) 



104. 2. Planorbis albus. Wliite Coil Shell. — 

 Shell thin, pellucid, white, concave, and with 

 the whorls equally convex on both sides, with 

 fine raised hispid spiral striae; mouth round- 

 ish-rhombic, (t. 8. f. 97.) 



Planorbis albus. JlluUe?; Verm. ii. 164. ; Leach, Syn. Moll. 

 113.; JefjFrerjs, Linn. Trans, xvi. 387.; Turt. Man. ed. 1. 

 114. f. 97. ; Forbes and Hanley, B. M. iv. 149. t. l-'6, f. 1, 2, 



— Helix alba. Mont. p. 459. t. 25. f. 7. — Planoi-bis hispi- 

 dus. Drap. Hist. p. 43. t. 1. f. 45—48.; Brard, p. 159. t. 6. 

 f. 6, 7.; Lam. Moll. vi. 154. — Planorbis villosus. Poiret, 

 Prod. — Planorbis liirsutus. Goidd, Inv. Mass. 206. f. 138.? 



— Gyrulus hispidus. Hartm. Gast. t. 25. 



In stagnant waters, on aquatic plants. 



Animal greyish. {Sturm, t. 42.) 



Shell about a quarter of an inch in diameter, very 

 thin and brittle, pale horn-colour, marked with very 

 fine close-set raised circular striae, which are clothed 

 with deciduous bristles, and crossed with obscure 

 longitudinal lines ; volutions five, the first very large 

 and rounded ; the upper surface a little sunk in the 

 middle, the under side more strongly concave ; aper- 



