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

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 Family Columellaria, (distinguished by a plaited columella.)

 Family Purpurifera, (yielding a purple colour.)

 Family Alata, (winged.)

 Family Canalifera (having a canal at the base of the opening.)

Family CONVOLUTA.

The convoluted shells contain but few genera; but these are very rich in species, and furnish us with some of the most beautiful specimens of this class.

FEEDERS ON ANIMAL FOOD, (Zoophagi.)

Lamarck notices no less than 181 recent species of the Cone shell. The Marbled Cone figured below, is found in most of the Asiatic seas, and is not uncommon; it is of a dusky colour, and covered with angular white spots. The section of this shell points out in a remarkable manner the economy and providence of the Creator, so visible in all his works.

Voluta diadema.Conus marmoreus. Columbella mercatoria.

It will be seen on referring to the engraving, that the shell is much thicker in the outward part of its coat than in any other part; and this exceeding thickness is necessary for the protection of the soft body of its inhabitant. In the course of the growth of the animal the shell is enlarged, and that part that was external becomes internal, the last made portion of the shell forming the outer wall; if, therefore, the inner part of the shell retained its original thickness, its weight would become too great for its possessor. To guard against this inconvenience, and this useless waste of material, the creature possesses the power of absorbing so much of the substance of what now becomes the internal portion of its dwelling as is unnecessary for its present use, and of re-depositing the same on the outward wall of its mansion, where strength is most required[1].