"I have heard that the Pinna is a shell-fish, attended by a crab, 'his cancer friend;' but why it is called anchor'd I do not know, but cancer is Latin for crab."
"Here is a species of Pinna," said his father, opening a cabinet; "and these silken threads are the means by which it fastens itself to the rocks. The animal is provided with a long foot, with which it draws out the threads, or byssus. The Pinna is sometimes called the silk-worm of the sea. Lucy, do you know a univalve shell?"
"Oh yes, many!" replied Lucy, "here are rock-shells, cowries, limpets, and cones. I know the difference between a cowry and a cone; but I am not yet acquainted with a multivalve shell—will you show me one?"
"Chiton, or coat of mail, is a good example," said Mr. Elliot; "Pholas is another genus of the same division; it has the appearance of a bivalve. In the Chiton are several lamina, or plates, which are connected by a membrane while the living animal is in the shell; the membrane is pliant, and the inhabitant has the power of contracting itself into a ball, when it would avoid injury, like the insect millepes, that we find under stones in damp places. ([Plate 2.]) The curious barnacle-shell, Lepas, is another multivalve." ([Plate 1.])
"I think we cannot have a more agreeable pursuit for our leisure hours," said Lucy, "than the study of shells. One can bring them out or remove them so easily, that they can cause little inconvenience, which garden-pots often do in town; and then the plants are almost sure to die, whatever care I take of them."
LAMARCK'S
SYSTEM.
"Collections of shells are frequently to be seen in London," said Mr. Elliot, "which are intended for sale. There are now many places where shells are sold at moderate prices, and young collectors like yourselves can easily avail themselves of the means thus afforded, to obtain even a single specimen. While we remain in town you may visit the British Museum, and become familiar with the rare species of each genus, of which there are many costly specimens. The arrangement adopted for that collection is Lamarck's. You will find the work of this celebrated naturalist on my shelves; it is entitled, 'Histoire Naturelle des Animaux sans Vertèbres.' The three last volumes contain the Conchology."
"It is in French and Latin!" exclaimed Lucy, as she opened a volume.
"Why do you both look so serious?" asked their father. "Are you not students in those useful languages? To what purpose do you learn a language if it be not with a view to reading the works of learned men, whose labours have opened a wide field of knowledge?"