SUMMARYTrichosarcina polymorphagen. et sp. nov. is newly described as a member of the Ulvales, Schizo‐meridaceae. The life cycle includes a uniseriate, Hormidiuzn‐like phase; a pluriseriate stage, and, finally, a chain of sarcinoidpackets which may dissociate. The cells are uninucleate, with a parietal cbloroplast and single pyrenoid. Quadriflagellate zoospores are produced singly by cells of the pluriseriate and sarcinoid stages. Sexual reproduction was not obser