A '''Shell''' is 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 | A '''Shell''' is 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 |