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Any mollusk which has a shell composed of more than two pieces.

Having many valves.

e or less covered and protected by a calcareous shell, which may be univalve, bivalve, or multivalve.

One of the pieces or divisions of bivalve or multivalve shells. Air valve, Ball valve, Check valve, etc. See under Air. Ball, Check, etc. -- Double-beat valve, a kind of balance valve usually consisting of a movable, open-ended, turban-shaped shell provided with two faces of nearly equal diameters, one above another,…