The little-known and rarely collected alga Exophyllum wentii Weber-van Bosse is re-described in detail from the type material, as well as from new collections from Indonesia, which for the first time reveal in detail the structure of cystocarpic and spermatangial plants and the development of tetrasporangial stichidia under culture conditions. New morphological reproductive information confirms placement of the genus Exophyllum within the Rhodomelaceae. Exophyllum is distinguished from other related genera within the Rhodomelaceae by its cartilaginous, non-trichoblastic decumbent thallus with multiple holdfasts and its discoid spermatangial organs. Some Pacific material earlier attributed to E. wentii was found to be misidentified and re-assigned to the Dasyaceae
