Читать книгу The Book of Shells. Containing the Classes Mollusca, Conchifera, Cirrhipeda, Annulata, and Crustacea онлайн

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The second Division of the objects of natural history, namely, the Invertebral animals, which we have now to describe, are placed by themselves, on account of their being without an internal skeleton, consisting of a series of vertebræ, or bones of the back. This distinction is explained in the introductory chapter to the Book of Animals. They have been separated, by Lamarck, into Eleven Classes, namely:—

1. Mollusca, (soft-bodied animals,) in general covered with a shell; as, for instance, a snail; or without a shell, as a slug.

2. Conchifera, (shell-bearing animals,) with a shell, consisting of two valves, as an oyster or mussel.

3. Cirrhipeda, (with feet like cirri, or hairs.) The inhabitant of the acorn-shell, found on the back of the larger kind of shell-fish, &c., is an instance of this class.

4. Annelida, (with body formed of rings;) of this class the leech and the earth-worm are instances.

5. Crustacea, (covered with a hard case,) crabs, lobsters, &c.

6. Arachnidæ, Spiders.

7. Insecta, Insects. A perfect insect has always six legs.