PLANORBIS. 
237 
Var. L, shell smaller, with the transverse laminje more re- 
mote : Planorbis cristatus. Drap. Hist, p. 44. t. 2. f. 1 — 3. 
Var. 2., with the transverse lamina© obliterated. 
Monstrosity, with the volutions detached and raised above 
each other. 
In ponds and ditches, on aquatic plants. 
Animal grey. 
Shell the tenth of an inch in diameter, of a black- 
ish or greenish horn-colour, with three volutions; 
the epidermis raised into numerous transverse ridges, 
which form a spinous crest round the outer margin ; 
aperture roundish-oval, united all round, and often 
detached from the second volution at its narrower 
end. 
M. de Quatrefages observes that, if a young Pla^ 
norhis imbricatus is examined with a weak magni- 
fying power, red blood is to be seen to fill the cavity 
of the pericardium and the ventricle, and at moments 
to colour the general cavity of the whole body on its 
lower surface ; he has not seen any distinct globules 
in this blood ; other specimens of a very small size 
have colourless blood. {Ann. and Mag, N. H. xvii. 
454, 1844.) 
c. Spire flat; whorls flat above ^ heeled. (Gyrorbis.) 
107. 5. Planorbis carinatus. Carinated Coil Shell. 
— Shell horn-colour, transparent, striate, near- 
ly flat above, rather convex and with a slight 
central umbilicus beneath ; whorls six, rapidly 
enlarging, with a prominent obtuse keel in the 
middle; mouth angular, (t. 8. f. 89.) 
Planorbis carinatus. Milller,^ Verm. ii. 157.; Drap. p. 46. t. 2. 
f. 13, 14. 16.; Brard^ p. 150. t. 6. f. 3.; Turton^ Man. ed. 1. 
