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Abstract
The morphology and fine valve structure of the marine attached diatom Cocconeis pseudomarginata Gregory var. intermedia Grunow was investigated. The entire frustule, internal and external structures of the raphid and araphid valves and complete cingulum are described using not only the light microscope and scanning and transmission electron microscope but also bleaching method and the focused ion beam technique. The raphe that terminates with a comma-shaped helictoglossa internally is slightly sigmoid. The hymenes, with perforations arranged in a centric array, are located near the internal openings of the areolae in the raphid valve (RV). The striae in the araphid valve (AV) consist of alveoli occluded by hymenes that have perforations arranged in a parallel array and locate near the outer surface. The complete cingulum of AV consists of an afimbriate, open valvocopula and two bands with small ligula. The RV has only a valvocopula which is open type and not fimbriate.