Chitin was found in the periderm of hydroids, the support of the sail of Vellela, shell and bristles of brachiopods, body wall of a Solenogaster, mantle epidermis of chitons, radula of slugs; but not in medusae, nematocysts, entoprocts, cyclostomatous ectoprocts, tube of a pogonophore, jaws of Nereis, a sipunculid, or the operculum of gastropods.