During a detailed study on the marine plankton of the Egyptian waters, the dinoflagellate species Ceratlum egyptiacum Halim was recorded from the south-eastern Mediterranean waters at Port Said and the sea area to the East. This species was recorded in the Suez Canal by Ghazzawi (1936) who wrongly identified it as C. pulchellum f. eupulchellu. Halim (1963) described it from a surface plankton haul sampicu in Lake Timsah in June 1957, and identified it as a new species (C. egyptiacum). The species was also reported (as/. suezensis) from the Suez Bay plankton (Halim, 1965) outside these two localities the species is not reported, as yet, from any other- sea area. It occurrence in the eastern Mediterranean waters is thus a new record to h., sea. The pattern of distribution of the species in the Mediterranean waters (both seasonal and spatial) may throw some light on the current regime in the area and on the dynamics of immigration planktonic organisms through the Suez Canal, particularly after the completion of the Aswan High Dam .

The data presented in this paper is based on the examination of more than 320 plankton samples collected on various occasions from the Red Sea, Suez Canal and Mediterranean waters of Egypt. Details of these samples are given in the text.