A terrestrial shell, distinguished from the Helix by its transverse
callous columella; depressed and diminished in thickness at the lower
part.
Shell sub-globular or conoid, spire low, a little depressed; aperture
semi-ovate, modified by the last turn of the spire; the edge of the
aperture sharp or a little reflected in a roll, the left edge enlarged
at its base in a large callosity, which entirely covers the umbilicus
and joins obliquely with the columella, which is twisted and a little
projecting; the operculum horny, complete, sometimes calcareous
externally.
Helicina Neritella.
H. striata.
H. fasciata.
H. viridis.
_H. Neritella._ The Nerite-shaped Helicina. Pl. 19, fig. 4.
Species yellowish white, finely striated, the edge reflected in a roll.
_H. striata._ The striated Helicina.
Globular, striated, the right edge sharp, but reflected; the umbilical
callosity rather thick, the operculum calcareous and solidified by a
marginal roll and a vertical crosspiece.