Rhodosorus marinus, Coccolithus neohelis, Ochrosphaera verrucosa, and Sarcinochrysis marina were isolated into culture from coral fragments and are recorded as new for the benthic marine algal flora of Hawaii. The life histories and cytology of these species were studied in culture. C. neohelis has no flagellated phase; the benthic stage consists of coccolith-bearing cells that reproduce solely by binary fission. O. verrucosa consists of a nonmotile colonial phase which does not produce coccoliths. Biflagellate coccolith-bearing zoospores that apparently lack a haptonema are derived from the colonial phase and germinate immediately to re-establish that phase.