FAMILY LYMN^EACEA. 143 



ture. The shell of P. carinatus is moreover paler in colour and 

 more glossy. There appears to be scarcely any appreciable diffe- 

 rence in the animals of the two species : both are violet-red, more or 

 less speckled with black, with long and slender tentacles. 



P. carinatus is much less generally diffused than P. complanatus. 

 It occurs, however, in many wide-spread localities in England, be- 

 coming gradually more plentiful towards the eastern and south- 

 eastern counties. 



6. Planorbis complanatus. Smooth Planorbis. 



Shell ; depressed, moderately concave above, the spire but Little 



immersed, concavely flattened below, dingy 



horny, rather rough, whorls five, rounded above, 



convex below, strongly keeled at the lower edge ; 



aperture obliquely ovate, somewhat rhomboidal. 

 Helix complanata, Linnaeus (1758), Sgst. Nat. 10th edit. 



p. 769 (not of Montagu). 

 Planorbis umbilicatus, Miiller (1774), Verm. Hist, part ii. 



p. 160. 

 Planorbis complanatus, Studer (1789), Faun. Helv. in Coxe, 



Trav. Sivitz. vol. iii. p. 435 (not of Poiret nor Draparnaud). 

 Helix lacustris, Razouniowsky (1789), Hist. Nat. Jorat, vol. i. p. 273. 

 Planorbus marginatus, Draparnaud (1805), Hist. Moll. p. 45. pi. ii. f. 11 to 



13. 

 Helix cochlea, Brown (1818), Mem. Wern. Soc. vol. ii. p. 501. pi. xxiv. 



f. 10. 

 Helix rhombea, and terebra Turton (1822), Conch. Diet. p. 47. 

 Planorbis rhombeus, Turton (1831), Man. p. 108. 

 Planorbis Sheppardi, Leach (1831), Turt. Man. p. 140. 

 Planorbis (Ggrorbis) complanatus, Moquin-Tandon (1855), Hist. Moll. 



vol. ii. p. 428. pi. xxx. f. 18 to 28. 

 Hab. Throughout Europe. Siberia. North Africa. England and Ireland. 



(Everywhere present in marshes, ponds, canals, ditches.) 



The shells of this and the preceding species, though resembbng 

 each other closely in general appearance, were well distinguished 

 by Linnseus. In P. carinatus {Helix planorbis, Linn.), the keel is 

 nearly central ; in P. complanatus {Helix complanatus, Linn., but 

 more generally known to collectors as P. marginatus, Drap.), the 

 keel is quite on the basal edge of the whorl. The name complanatus 



