The structure of a new citraconic anhydride derivative from Piptoporus australiensis is established by spectroscopic and chemical methods as 3-[(7Z)-hexadecenyl]-4-methylfuran-2,5-dione; Sixty-seven compounds were characterized in the wax of Sargassum fulvellum. Characteristic components were the 5-methylhexyl esters of octanoic, decanoic, lauric, myristic, palmitic, palmitoleic, stearic, oleic, linoleic and linolenic, and the 2-ethylhexyl esters of the same acids. The wax of S. fulvellum contains hydrocarbons (1.6%), esters (21.8%), free acids (74.9%) and free alcohols (0.3%). The principal free alcohols range in chain length only from C₁₄ to C₁₆.