Twelfth Class—Mollusca.
"As I have observed that you have been very diligent in studying Lamarck since our last lesson," said Mr. Elliot, "I propose to make you acquainted with the variations in the univalve genera.
"The animals of the Mollusca are soft, without joints, generally possessing a head, eyes, and tentacula, or feelers. They have also a fleshy membrane, called a foot, which they use for climbing. The orders, excepting the first, are named from the position of this foot. They are five in number. The first order contains very few genera. One genus, named Cleodora, contains a species brought from Africa. The shell is curious, transparent, and shaped like the head of a halberd.
"The animals of the second order, Gasteropoda, have a muscular foot, or disk, on which they rest. The families are seven. The first, Tritonia, I shall pass over.
"Phyllidiana includes the genera—
| Phyllidia. | |
| Chitonella. | |
| Chiton | Coat of mail. |
| Patella | Patella, or limpet. |
CHITON.
PATELLA.
"The Chiton moves like the Patella, upon a disk, or foot.
"The body of Patella is entirely covered by the shell. You may have many opportunities of examining the British species. P. pellucida is very transparent, with blue lines.