A new brackish water diatom, Achnanthes secretitaeniata, from Japan

A new monoraphid diatom, Achnanthes secretitaeniata, is decribed from brackish water in the coast, Yamada-machi, Shimohei-gun, Iwate Pref., Japan. Cell shape is more or less linear with rounded extremities. Rapheless sternum grows close to the margin of the araphid valve. Araphid valve margin is well developed, but does not form marginal ridge as in A. yaquinensis and A. subconstricta. Valvocopulae and copulae are open- ended at both poles of valve. This species is closely related to A. brevipes C. Agardh var. intermedia (Kütz.) Cleve, but, they can be easily distinguished from each other by the position of rapheless sternum and the structure of valve margin on their araphid valves.