"In the next family, Alata, we must notice a remarkable fact: the shells, while they are young, assume a different form to those more advanced in growth.
ROSTELLARIA.
PTEROCERA.
STROMBUS.
"The genera are three—
| Rostellaria, | } | Strombus, wing-shell. |
| Pterocera, | ||
| Strombus, |
"In the first genus the shells are terminated below by a canal, or pointed beak; the right-margin entire, or toothed, more or less dilated with age, and having a sinus contiguous to the canal. There is a specimen from our own coast, Rostellaria pes-pelicani, the pelican's-foot: it was Strombus of Linnæus. ([Plate 7.]) There are many of this species found in a fossil state.
"The Pterocera genus is easily known by the digitated, or fingered, appearance of the right-margin. The greater part of the species become very large. Here we find the scorpion, with seven digitations, from India; the spider, with the same number, a large and fine shell, also from India.
"Strombus has a short canal, the right-margin dilated with age into a simple wing, having, at the lower part, a sinus, separated from the canal at the base of the shell.
"All the species are natives of hot climates; some attain a very large size, such as S. gigas, so frequently seen in shops, and as ornaments in a room. S. gibbèrulus is a pretty little shell; the white, gibbous whorls render it remarkable; the interior of the lip is pink. S. lineàtus has dark lines round the shell. S. vittàtus has a very long spire; the colour is tawny, girded with white: you may easily meet with this species.
CASSIDARIA.
CASSIS.