Two new species of Dictyota (Dictyotales, Phaeophyta) from the Indo-Malayan region

Two new species of Dictyota (Dictyotales, Phaeophyta) are described from th e Indian Ocean, Indonesia, and Papua New Guinea. Dictyota grossedentata is a procumbent species with large, irregularly placed marginal teeth, differi ng from all other prostrate species by its stout habit and conspicuous dent ation. Dictyota grossedentata differs from other species characterized by d entate margins by its prostrate habit and by the lack of a single, conspicu ous stupose base. Dictyota rigida is a stiff, completely erect species with a single point of attachment. Because of its stiff texture, it resembles D . fastigiata Sender and D. suhrii Murray but differs by its unilayered medu lla. Dictyota rigida also is compared with the other slender taxa. Taxonomi c problems of the genus, such as substantial morphological variation and a lack of clearly discriminating characters, are considered.