INHABITANTS
OF SHELLS.
"Conchology," said Mr. Elliot, on resuming the conversation with his children, "is that branch of natural history which comprehends the study of testaceous animals, or animals with shell-coverings, and includes those of the seas, the rivers, and the land.
"All shells are formed of carbonate of lime. This you may easily prove by applying a little acid to a shell, and you will find that an effervescence takes place.
"The animals that inhabit shells are bloodless, without bones, but provided with a heart, lungs, and mouth, together with other organs needful to their conformation.
"Testaceous animals have the power of enlarging their habitations; they can also repair any injury that may occur to them.
"Many kinds of shell-fish are made use of by man, and form a valuable article of food, such as oysters, cockles, muscles, scallops. The whelk is also used, and a species of murex.
"A species of cowry is in use for money among some people of Africa; and pearls, so much valued as articles of ornament, are obtained from the oyster and mussel genera.
FOSSIL
SHELLS.
"Within a few years, conchology has become a study of considerable importance, from its close connexion with geology. Students in the latter science must be well acquainted with fossil-shells, because they form so large a portion of organic remains. Species of recent shells, or those still existing, are also often found in a fossil state, while many fossil genera are now totally unknown in our earth and waters.
"Thus you perceive that while you are obtaining knowledge in one science, you are preparing yourselves for making advances in another, most interesting and wonderful. You, Charles, who are likely to become a traveller, will perhaps in future years find the advantage of my present brief lessons.