234 LIMNJEAD^E. 



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 ; whorls crested or ciliated; 

 mouth roundish. (Gyraulus.) 



104. 2. PLANORBIS albus. White 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. Mutter, Verm. ii. 164. ; Leach, Syn. Moll. 

 113.; Jeffreys, Linn. Trans, xvi. 387.; Turf. Man. ed. 1. 

 114. f. 97. ; Forbe* and Hanley, B. M. iv. 149. t. 126. f. 1, 2. 



Helix alba. Mont. p. 459. t. 25. f. 7. Planorbis hispi- 

 dus. Drop. Hist. p. 43. t. 1. f. 4548.; Brard, p. 159. t. 6. 

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

 Prod. Planorbis hirsutus. Gould, 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- 



