68 The Shell-Collector’s Handbook. 
PLANORBIS CARINATUS, MULLER. 
SHELL nearly flat above, rather convex below, gradually 
shelving to the outer edge, thin, glossy, yellowish horn- 
colour; whorls five to six, the outer one growing suddenly 
larger ; suture deep; periphery prominently keeled in the 
middle line; mouth obliquely oval, somewhat angular; 
umbilicus small, central. Animal deep reddish-brown, 
‘indistinctly spotted with black. 
Habitat.—Stagnant waters, and sluggish rivers. 
v. disciformis (Jeff.): Shell flatter and thinner, of 
a yellowish colour, having the last whorl larger in pro- 
portion to the others, and the keel more prominent and 
sharp, and placed exactly in the middle. (Jeffreys, Linn. 
Trans. Xvi., pp. 385 and 521). 
v. albida (Hudson): Shell pellucid white. 
PLANORBIS COMPLANATUS, LINN. 
SHELL brown horn-coloured, striolate, slightly concave 
above, flattish, with a central concavity below ; whorls five 
to six, rapidly enlarging, ventricose, the diameter of the 
body whorl being equal to one-fourth of the whole; periphery 
strongly keeled below; suture deep; mouth rhombic, 
rounded in front, often ribbed internally ; umbilicus large 
and very shallow. Diameter of shell # of an inch. Animal 
deep violet-red, finely speckled with black. 
Habitat.—Ponds, canals, ditches, and slow rivers. 
v. rhombea (Turton.): Shell smaller, more convex 
above, with: a deep concavity beneath, and a blunt keel. 
Helix rhombea, Turton., Conch. Dict. p. 47. (Possibly these 
are the young of P. complanatus, and not a variety 
at all). 
v. albina (Jeff.): Shell whitish or colourless. (B. C. 
vol. 1.,,p. 91). 
m. terebrum (TZurton.): Whorls dislocated from one 
