LYMN^CEA. 21 



First Ed., pi. 41, f. 39, 40, 41; Alder, Mag. Zool. and Bot., II, 

 p. 112; Turton, Man., p. 107, f. ^1 ',-^ Planorhis complanatus, 

 Turton, Man., p. 108, f. 88 ; Fleming, Brit. An., p. 278; Helix 

 planorhis, Pennant, Brit. Zool., II, pi. 83, f. 123; Maton and 

 Racket, Linn. Tr., VIII, p. 188, pi. 5, f. 13; Helix complanata, 

 Montagu, Test. Brit., p. 450, pi. 25, f. 4; Planorhis umhilicatus, 

 Muller, Verm., II, p. 160; Jeffreys, Linn. Tr., XVI, p. 384. 



It is subject to the following varieties. 



Variety 1. Sides unequal, fragile, and glossy. 



Planorhis turgidus, Jeffreys, Linn. Tr., XVI, p. 383. 



Variety 2, the young shell, pi. IV, f. 5, 6, Brown, Illust. 

 Conch., p. 32, pi. 18, f. 24; Planorhis rhomheus, Turton, Man., 

 p. 108, f. 90; Planorhis Sheppardi, Leach, Moll., p. 149; 

 Planorhis Drajjernaldi, Jeffreys, Linn. Tr., XVI, p. 306 ; 

 Helix Drapernaldi, Sheppard, Linn. Trans., XIV, p. 158. 



Variety 3. Destitute of a heel. 



Shell of a brownish horn-colour, semitransparent, slightly 

 striated transversely, flat, or somewhat concave above, subum- 

 bilicated below ; with five or six rapidly increasing, flat volu- 

 tions, with a strong carina above, and ventricose and rounded to 

 the margins beneath ; aperture rhombic, with the front rounded. 

 Three-quarters of an inch in diameter. 



Found in stagnant waters all over Great Britain and Ireland. 



This is to be distinguished from P. carinatus by its being 

 thicker, and the volutions more rounded, and more convex 

 beneath on the margins ; in its more rounded aperture ; and in 

 the keel being less prominent. 



The young shell is more rhomboidal, with the edges consi- 

 derably thicker in proportion to its size, and is described and 

 figured by Turton as a distinct species, under the name of Pla- 

 norhis rhomheus. 



A remarkable monstrosity of this species was found by Mr. 

 Thomas Stephens, in the pond of the College Botanic Garden 

 of Dublin ; and is in the cabinet of my respected friend M. J. 

 O'Kelly, Esq., of Rochestown House, near Cabinteely, Ireland. 

 Plate III, f. 29. 



I figured and described this monstrosity in the Wernerian 

 Memoirs, vol. II, p. 528, pi. 24, f. 10, under the name of Helix 

 cochlea. It is thus described : — 



