Читать книгу The Book of Shells - Society for Promoting Christian Knowledge . Committee of General Literature and Education - Страница 11

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The Trachelipodes contain by far the largest portion of the univalve shells, and are mostly inhabitants of the waters. They form two numerous groups, the feeders on animal food, (Zoophagi,) and those that exist on vegetable substances, (Phytophagi.) The animal feeders are well distinguished from the other group, by having a mouth without jaws, being furnished with a tube which they can retract or advance at pleasure, for the purpose of sucking their nutriment from the bodies of other inhabitants of the deep. The animal feeders are also known from the other section by the possession of a projecting tube called a siphon, which conveys the water to the gills. The shell also points out to which section its possessor belonged, from the lower part of its opening being formed either into a sort of canal, or a groove for the reception of its siphon. They are all marine animals, and breathe water. The flesh-eating tribes compose five families.

 Family Convoluta, (rolled up like a scroll.)

 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.