66 The Shell-Collector’s Handbook. 
ridges, and larger than the rest of the shell; mouth, 
oval; umbilicus large. Diameter of shell ;,th inch. 
Animal grey, marked with minute black specks. 
Hatitat.—In still waters on aquatic plants. 
v. crista (Zinn.): Shell with the transverse ridges 
more pronounced, and with the periphery deeply notched 
or crested by them. (= Nautilus crista. Linn., Syst. Nat. 
ed. x., 1758.,1., p. 709. Planorbis cristatus., Drap., Hist. 
Moil., 1805, p. 44, pl. i1., figs. 1-3.) 
PLANORBIS ALBUS, MULLER. 
SHELL thin, pellucid, whitish, convex above, concave 
below, finely striated longitudinally, and marked with very 
fine close-set raised circular strize which are clothed with 
deciduous bristles ; whorls five, the last one being dispro- 
portionally enlarged; mouth roundish-oval: umbilicus 
large. Diameter of shell { inch. Animal greyish-white, or 
greyish-brown; tentacles pale grey, with a central brown 
line ; foot narrow, dark reddish-brown. 
Habitat.—Lakes, ponds, and stagnant water. 
v. draparnaldi (Shepp.): Shell more closely striate in 
line of growth; periphery distinctly carinate ; umbilicus 
deeper. (=P. spirorbis. Drap. Hist. Moll. p. 45, pl. ii, f. 
8-10.—Helix Draparnaudi, Sheppard. Linn. Trans, xiv., 
p. 158.) 
PLANORBIS GLABER, JEFFREYS. 
SHELL somewhat convex above, with a central depression, 
concave below, smooth, semitransparent, brownish horn- — 
coloured; whorls five, rounded, and having the upper side 
more convex than in P. albus, the body whorl occupying 
nearly one-half of the shell; mouth nearly circular; 
suture well pronounced; umbilicus large; circular striz 
absent. Body yellowish-grey. 
Habitat.—Ponds, marshes, and lakes. 
