138 



BRITISH MOLLUSKS. 



f. 13. 



1. Planorbis corneus. Homy Planorbis. 



Shell ; stout, rather ventricose, livid ash, greyish olive, or white, 



more concave above than below, the 



spire being conspicuously immersed, 



whorls five to five and a half, glossy, 



densely transversely striated, longitu- 

 dinally striated while young, then 



faintly malleated; aperture obliquely 



lunar-rounded, outer lip a little ex- 

 panded, not reflected. 

 Helix cornea, Linnaeus (1758), Syst. Nat. 10th 



edit. p. 770 (not of Drapamaud). 

 Planorbis purpura and similis, Muller (1774), 



Verm. Hist, part ii. p. 154 and 166. 

 Helix nana, Pennant (1776), Brit. Zool. ed. iv. 



toI. iv. p. 133. pi. lxxxiii. f. 125. 

 Helix comu-arietis, Da Costa (1778), Brit. Conch, p. 60. pi. 

 Planorbis corneus, Poiret (1801), Coq. de V Aisne, Prod. p. 87. 

 Planorbis Metidjensis, Forbes (1838), Moll. Alg. Ann. Phil. p. 254. pi. xii. 



f. 5. 

 Planorbis Dufouri, Graells (1846), Cat. Moll. Es-pan. p. 11. pi. i. f. 11 to 



15. 

 Planorbis (Coretus) corneus, Moquin-Tandon (1855), Hist. Moll. vol. ii. 



p. 445. pi. 31. f. 32 to 38 and pi. xxxii. f. 1 to 6. 

 Planorbis Etruscus, elophilus, Nordenshioldi, anthracius, Banaticus, ade- 



losius, and aclopus, Bourguignat (1859), Rev. et Mag. de Zool. no. 12 ; 



Amen. Malac. vol. ii. p. 127 to 135. pi. xvi., xvii. 

 Hab. Pretty general in Europe. Siberia. North Africa. South-eastern, 



eastern, and midland counties of England. (In muddy ponds and 



ditches.) 

 This well-known species stands conspicuously alone in the series 

 on account of its colossal dimensions when compared with any other 

 European form of Planorbis. It is indeed the largest in any part 

 of the world, though nearly equalled in size by one or two Brazilian 

 and West Indian species. The animal, as represented of the 

 natural size in our vignette, is of dark reddish black, sluggish in its 

 movements, mostly swimming at the under surface of the water in 

 a half- contracted state, but very irritable ; and when irritated or 

 wounded it will emit a purple fluid. The shell is rather inflated 

 in growth, and has the surface faintly malleated as well as densely 

 transversely striated, and towards the apex, where the early growth 

 of the shell is seen, it is strongly striated longitudinally. The mal- 



