LIMNiEADuE. 269 



tral sunk spire, rather convex beneath; whorls 



three or four, the outer shelving to a keel in the 



middle; mouth elongate-angular. 

 Planorbis complanatus. Drap. p. 47. t. 2. f. 20 — 



22. Rossm. Icon. ii. 16. t. 7. f. 116. ; Brard, 



p. 161. t. 6. f. 4. 

 Helix fontana. Lightf. Phil. Trans, lxxvi. t. 2, 



f. 1. ; Montagu, p. 462. t. 6. f. 6. 

 Planorbis nitidus. Muller, Verm. ii. 263. (part) — 



Fleming, B. A. 278.; Jeffreys, Linn. Trans, xvi. 



389.; ^<?r, Mag. Z. 8? B. ii. 114. 

 Planorbis lenticularis. V. Alten ; Sturm, Fauna, 



vi. 8. 16. 

 Planorbis fontanus. Turton, Man. ed. 1. 110. f. 93. 

 Helix lenticularis. V. Alten, 35. t. 2. f. 4. 



In clear stagnant waters, on aquatic plants. 



Animal black. 



Shell not a quarter of an inch in diameter, of a dark 

 wgfo or whitish horn-colour, very convex be- 

 neath, with the centre flattened, above flat, 

 with a central umbilicus ; the outer volution slightly 

 but rather sharply carinate near the middle; the 

 front of the shell is regularly convex, has the appear- 

 ance of being the proper spire, as in Segmentina. 

 This shell differs greatly in size and colour ; the larger 

 specimens are generally much the darkest, being often 

 reddish brown. 



n 3 



