Stephanodiscus hitaensis sp. nov., a new diatom species from a Pleistocene deposit of western Oita, Kyushu, Japan

抄録

Stephanodiscus hitaensis H.Tanaka & Nagumo sp. nov., is characterized by one valve face fultoportula located in the middle of the valve center surrounded by other fultoportulae arranged in a circular pattern. Two, sometimes three, rimoportulae with external tubes are situated on the valve face/mantle junction at the end of interfascicles. Spines are thick, bent almost in half with the upper portion flat toward the valve. The new species is shown with LM and SEM photographs. The material was taken from the Lower to Middle Pleistocene lacustrine sediment of the Oyama Formation, Hita City, Oita Prefecture, Kyushu, Japan.