"The Turbinacea family contains many genera, with which you will soon become familiar. I believe you are already acquainted with this shell, which, from the time it was first known to collectors, has always been celebrated for beauty. It is now called Solarium perspectivum. ([Plate 9.]) The large, spiral, crenated umbilicus is its great peculiarity. The French call the shell Cadran, dial. In its natural state the shell is covered with an epidermis. There are a few fossil species, one in the oölite of our own country. The English name is staircase trochus.
ROTELLA.
TROCHUS.
TURBO.
"The genera of Turbinacea are,
| Solarium | Trochus. |
| Rotella | Trochus—wheel-shell. |
| Trochus | Trochus—top shell. |
| Monodonta. | |
| Turbo | Turbo. |
| Planaxis | Buccinum. |
| Phasianella | Turbo. |
| Turritella | Turbo. |
"The genus Rotella contains small, flattened, wheel-shaped shells, common in most collections. They are smooth and polished.
"Trochus is still a large genus. Trochus marmoràtus is a fine species from the Indian Ocean. There are several handsome species on our own shores. T. magus is one of them; it has a large, deep umbilicus, or perforation; the spire is flattened; the whorls are crowned with tubercles. The Trochi of tropical climates are thinner than those of northern latitudes.
"When any of these shells are placed upon their base, their axis is always inclined: of course they never stand perfectly upright.
"There are several fossil species.