Abstract
Cyclotella kohsakaensis Tanaka & Kobayasi, sp. nov. is described: It was taken from a silt stone sample in a Kohsaka Conglomerate Member. The age of the material is assumed to be from the Pliocene Era based on the plant fossils in the stratum. This new species is characterized by its smooth central zone without fultoportulae or rimoportulae but with undulation, and by the marginal fultoportulae and rimoportulae on the depressed ribs, and the stria composed of the same size areolae arranged in hexagonal array.
