1834, Georges Cuvier (baron), Edward Griffith, Charles Hamilton Smith, The animal kingdom arranged in conformity with its organization The naked mollusca are those in which the mantle is simply membranous or fleshy: most frequently, however, it forms in its thickness one or several laminae, of a substance more or less hard, deposited in layers, and increasing in extent, as well as in thickness, because the recent layers always outedge the old ones.
Source: wiktionary