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1. Any of various small marine clams of the genus Donax having variously colored, often striped or banded wedge-shaped shells, and found especially on sandy beaches along the Atlantic coast of the United States.
2. A soft porous limestone, composed essentially of fragments of shells and coral, used as a building material.
[Spanish, cockle, probably diminutive of concha, shell, from Latin, mussel; see conch.]
(Geological Science) a soft limestone consisting of shells, corals, etc, that occurs in parts of the US
[C19: from Spanish: shellfish, probably from concha shell, conch]
n., pl. -nas.
1. Also called butterfly shell. a small clam, Donax variabilis, having fanlike bands of various hues and common in intertidal zones of the E and S U.S. coasts: the paired empty shells often spread in a butterfly shape.
2. any similar clam.
3. a soft whitish rock made up of fragments of marine shells and coral, used as a building material.
A brittle limestone made of shells and shell fragments.