"The Nerìta genus is very pretty: (Plate 7.) the texture of the shell is in general much thicker than that of Helix. The shell is spiral, gibbous, pillar-lip transversely truncated, flattish. Seventy-six species. Nerìta polìta is a handsome species: those most valued are from the South Sea.
"We have now lost sight of the pillar-lip, and in the genus Haliòtis we find a flat, ear-shaped shell, the spire nearly hidden, the disk perforated lengthways with pores. Species twenty-one. The animals that inhabit the ear-shells fasten themselves so firmly to the surfaces of rocks, that much force is needful to disengage them: during the fine nights of summer, the animal feeds on the herbage that grows on the sea-shore. The sea-ear from New Zealand, and that from California, are superb shells of considerable size. The British species, Haliòtis tuberculàta, is not uncommon. ([Plate 8.])
Without a regular spire: 5 genera.
PATELLA.
DENTALIUM.
SERPULA.
"You are well acquainted with Patella, the limpet: one species of this genus is very common on the rocks by the sea-side. ([Plate 1.]) In the Patella genus we lose sight of a spire; the shell is nearly conic, and shaped like a basin. The species are very numerous, exhibiting great variety of form; the number is two hundred and forty.
"The form of Dentalium is easily known. The shell is univalve, nearly straight, tubular, not chambered, and open at both ends.
"The species called elephant's-tooth is slightly curved, the colour green, ([Plate 2.]) It is found in the European and Indian seas. There are only twenty-two species. Dentalium entails, the dog's-tooth, is very common.
"The Serpula genus is remarkable. The shells are tubular, frequently closed at one end. They are often found in clusters, adhering to rocks, stones, fuci, shells, &c.
"There is Serpula triquetra upon a pecten, ([Plate 8.])