A tough, multilayered structure secreted by the mantle. It is usually used for protection, but sometimes for body support.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia
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A tough, multilayered structure [[secretion|secreted]] by the [[mantle]]. It is usually used for protection, but sometimes for body support.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia