This genus is generally heterostrophe (that is, with whorls turned to
the left hand); found in fresh water; it greatly resembles the Lymnæa,
but has not a widened aperture.
Shell often sinistral, oval, oblong, or globular, perfectly smooth;
aperture oval, contracted posteriorly; the right edge sharp, advanced
above the plane of the left edge; columella twisting obliquely, and
enlarging to join itself to the anterior part of the columellar margin.
Physa castanea.
P. fontinalis.
P. hypnorum.
P. subopaca.
_P. fontinalis._ The fountain Physa. Pl. 20, fig. 2.
Volutions reversed, oval, ventricose, pellucid, horn-coloured; spire
short and acute.