Formerly classed with the Helix, which it somewhat resembles in form,
but properly separated, as it differs in every other respect.
It is a singular marine shell, often found in great numbers floating on
the surface of the sea, suspended by a vesicular appendage, which stains
the hand of a purple colour.
Shell sub-globular, ventricose, extremely thin and fragile; transparent,
of a beautiful violet colour; the spire low, lateral, pointed, with
sub-carinated whorls; aperture large, sub-angular, greatly modified by
the last whorl of the spire; edges disunited, the left entirely formed
by the columella, which is straight and continued beyond the base, the
right edge sharp, often with a sinus in the middle.
Janthina communis.
Janthina exigua.
_J. communis._ The common Janthina. Pl. 18, fig. 6.
Very fragile, aperture triangular, with a small notch on the margin of
the outer lip; beautiful violet colour.
FAMILY XII.
MACROSTOMIDES. Four genera.