N. auriculata. The eared Neritina.
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.
N. perversa. The perverse Neritina.
Species shaped like a Calyptræa, with the superior summit vertical, spiral; the last whorl forming all the base of the shell.
2. Navicella. Three species.
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.
Navicella elliptica.
N. lineata.
N. tessellata.