LIMN^US. 
207 
tudinally, and generally crossed by raised transverse 
lines, giving it an angular appearance like cut glass ; 
pillar with the fold very strong, forming a slight um- 
bilicus, the lip white and spread. 
These shells vary greatly in thickness, according 
to the nature of the water they inhabit. The outer 
whorl of the adult shell is often very gibbous. These 
variations have caused the animal, when found in 
clear quiet water, to be considered as a separate 
species. 
Dr. Turton’s figure (Mayz. ed. 1. f. 102.) of Physa 
scaturiginum has been suspected to represent a young 
individual of this species. It is a copy of Drapar- 
naud’s, which is a very doubtful species ; and thought 
to be the young of some land shell. A reversed dis- 
tortion is sometimes found. {Hanov^ Seltenheiten^ ii. 
t. 1. f. 5.) 
Montagu erroneously thought that these animals 
were unisexual ; for he observes, the sexes, too, are 
distinct, as is usual in aquatic Limaces. 
The eggs are ovate, with a yellow spot ; they are 
united together into elongated subcylindrical or 
oblong masses, attached to water-plants, &c. (See 
Pfeiffer, f. 13, 14, 15.) 
Rossmasler has described a North American 
species, like the first variety, under the name of L. 
speciosus. (t. 2. f. 50.) 
M. Prevost has remarked that the impregnation 
of these animals is only accomplished by the par- 
ticipation of three individuals; the middle one 
using the functions of both sexes, the two others 
that of the male and the female only. Sometimes the 
