A new sand-dwelling dinoflagellate, Gymnodium quadrilobatum sp. nov., is described from the south coast of Natal, South Africa. The organism contains 20-30 chloroplasts, which are peripherally arranged, and a conspicuous eyespot. The motile cell is directly transformed into a non-motile cell and cell division is restricted to the non-motile phase, The motile cell has a typical gymnodinioid organisation, while the non-motile cell possesses a thick cell wall and develops the characteristic cell shape, which is reminiscent of a four-leaved clover. The chloroplasts of G. quadrilobatum belong to an endosymbiotic alga the cytoplasm of which is separated from the host (dinoflagellate) cytoplasm by a single unit membrane. Other organelles contained in the endosymbiont cytoplasm are the nucleus, ribosomes and mitochondria. The endosymbiont is thought to be a chromophyte alga. The eyespot is bounded by a triple membrane and is situated in the host cytoplasm. On the basis of the similarities in the ultrastructure of G. quadrilobatum with those of four thecate dinoflagellates, viz. Peridinium balticum, P. foliaceum, P. quinquecorne and Peridinium sp., which are known to possess a similar endosymbiont, possible phylogenetic affinities between G. quadrilobatum and four thecate dinoflagellates are discussed.

A new dinoflagellate Durinskia capensis Pienaar, Sakai et Horiguchi sp. nov. (Peridiniales, Dinophyceae), from tidal pools along the west coast of the Cape Peninsula, Republic of South Africa, is described. The dinoflagellate produces characteristic dense orange-red colored blooms in tidal pools. The organism is characterized by having a eukaryotic endosymbiotic alga. Ultrastructure study revealed the organism has a cellular construction similar to that of other diatom-harboring dinoflagellates. The cell is thecate and the plate formula is: Po, x, 4', 2a, 6'', 5c, 4s, 5''', 2'''', which is the same as that of Durinskia baltica, the type species of the genus Durinskia. D. capensis can, however, be distinguished from D. baltica by overall cell shape, the relative size of the 1a and 2a plates, the degree of cingular displacement, and the shape of the eyespot. Our molecular analysis based on SSU rDNA revealed that D. capensis is closely allied to D. baltica, thus supporting the assignment of this new species to this genus. This Durinskia clade takes a sister position to another diatom-harboring dinoflagellate clade, which includes Kryptoperidinium foliaceum and Galeidinium rugatum. Molecular analysis based on the rbcL gene sequence and ultrastructure study revealed that the endosymbiont of D. capensis is a diatom. The SSU rDNA gene trees indicated that four species with a diatom endosymbiont formed a clade, suggesting a single endosymbiotic origin.

The taxonomy of Prymnesium (Prymnesiophyceae) including a description of a new cosmopolitan species, P.Patellifera sp. nov., and further observations on P.parvum N. carter, British

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