As early as 1927, Prof. M. O. P. Iyengar gave a brief account of the flora of Krusadai Island and other collecting grounds in the Gulf of Mannar and Palk Bay areas near Mandapam. Later on, Boergesen (1937a, b ; 1938) reported a large number of the algae occurring around Mandapam in his contributions on south Indian algal flora, but the green algae of this area were not included in this work. Since then, detailed attempts have not been made to study the algal flora of Mandapam, but for a provisional list of algae of Krusadai Island (Chacko et ah, 1955) and a paper on a new species of Halicystis (Iyengar & Ramanathan, 1954). While working on some ecological aspects of marine algae of Mandapam, the author had the opportunity to collect alga...