3. Pirena. Four species.
This shell resembles the Melania, but is easily distinguished by having a sinus at the base and another at the summit.
Shell turreted, aperture oblong, closed by a horny operculum; right lip sharp, with a distinct sinus at the base and another at the summit; base of the columella inclined towards the right.
Pirena terebralis.
P. spinosa.
P. aurita.
P. granulosa.
P. terebralis. The wimble Pirena.
Subulate, longitudinally striated, covered with a dark-brown epidermis; aperture white, outer lip expanded.