238 LIMN^AD^E. 



t. 16. f. 89. (not 87.); Leach, Syn. Moll. 114.; Forbes and 

 Hunley, B. M. iv. 153. t. 127. f. 4, 5. ; Ros&m. Icon. i. f. 60. 

 Helix carinata. Mont. T. B. 451. t. 25. f. 1. Helix 

 planata. Linn. Trans, viii. p. 189. t. 5. f. 14. Helix pla- 

 norbis. Linn. S. Nat. i. 124-2.; Turton, Diet. p. 45. (not 

 Da Costa}. Helix complanata. Mont. T. B. 450. t. 25. 

 f. 4. Planorbis complanatus. Turton, Man. ed. 1. f. 89. 

 (not description). Planorbis lutescens. Jeffreys, Linn. 

 Trans, xvi. 385. (not Lam.}. Planorbis planatus. Turton, 

 Man. ed. 1. 110. f. 92. Helix linibata. Da Costa, B. M. 

 63. t. 4. f. 10., t. 8. f. 8. Planorbis acutus. Poir. Prod. 91. 

 (not Drap.) Planorbis uiubilicatus. Studer, 92. (not 

 Miiller). 



Var. 1., keel more central, lower disk rather more convex : 

 Planorbis disciformis. Jeffreys, Linn. Trans, xvi. 521.; 

 Alder, Mag. Z. and B. ii. 113. 



In stagnant waters. 



Animal brown. 



The animal, according to Montagu, differs from 

 P. marginatus in the tentacles being somewhat longer, 

 and particularly in their being pellucid, yellow, and 

 not darker in the middle. ( T. B. 453.; Sturm, t. 43.) 



Shell hardly half an inch in diameter, with five 

 volutions, the outer one growing suddenly larger, 

 above nearly flat, beneath rather convex, gradually 

 shelving to the outer edge ; in the older specimens 

 the hinder or upper part of the whorls becomes rather 

 convex; colour pale horn-colour and transparent, 

 often covered with a brownish coat ; aperture con- 

 tracted to a point above, in consequence of the keel. 



This species is immediately known from Planorbis 

 complanatus by the under or front side of the whorls 

 not being so convex and ventricose, by their shelving 

 gradually to the outer edge, and by the hinder or 

 upper part of the whorls of the older shells being 

 rather convex, somewhat like the lower, which has 



