Species sinistral, with a very large umbilicus, spirally carinated.
Formerly classed with the Nerita, but separated from it because the Nerita is a marine shell, and those of this genus are fluviatile.
They are generally thin, smooth, or very finely striated; the right side of the aperture is not crenulated or dentated, and the animal dissolves the interior of the spire.
Shell thin, ovate, not umbilicated; aperture semilunar; inner lip reflected on the columella, and sometimes crenated; outer lip without teeth internally; operculum with a lateral tooth.
Neritina perversa. N. pulligera. N. dubia. N. zebra. N. zigzag. N. gagates. N. lugubris. N. corona. N. brevispina. N. crepidularia. N. auriculata. N. Domingensis. N. fasciata. N. lineolata. N. semi-conica. N. strigilata. N. meleagris. N. Virginea. N. fluviatilis. N. viridis. N. Bætica.
_N. fluviatilis._ The fresh-water Neritina.
Shell very small, oval; back convex, smooth, white, with black or brown spots; spire inclined, lateral lip slightly denticulated; right edge sharp, operculum very oblique.
_N. zebra._ The zebra or striped Neritina. Pl. 21, fig. 2.
Same as N. fluviatilis, but striped instead of spotted.
_N. corona._ The crown Neritina. Pl. 21, fig. 4.
Species provided with long spines, and with the columellar edge denticulated.
Species with the columellar edge denticulated; the two extremities of the right edge extending beyond the aperture, and forming with the callosity, which is reflected over the columella, a kind or ear, produced by the tentacular lobe of the animal.
Species shaped like a Calyptræa, with the superior summit vertical, spiral; the last whorl forming all the base of the shell.
A fresh-water shell, closely allied to the Neritina; it generally has the appearance of porcelain.
Shell ovate oblong, covered with epidermis, shaped like a Patella, summit not spiral, but straight, turned quite to the base, and concave beneath; no columella; the columellar edge replaced by a kind of sharp partition, which covers part of the aperture, with a sinus at its left extremity; muscular impression shaped like a horseshoe, open in front and interrupted behind; thin, calcareous operculum, with a subulate, lateral tooth adhering to the posterior margin; the other edges sharp.