Subgenus: Entomum (Apical area deeply indented or notched) Section: Incisa (Cell surface smooth; apical area without spiny projections) Species: Cell body elongated ellipsoidal, (115-162)-205 μm long, (60-78)-107 μm wide, L/W=2; semicells consisting of five lobes (one terminal, four lateral); bay opening between terminal and anterior lateral lobe is deeper and narrower than that between anterior and posterior lateral lobes; terminal lobe laterally extended forming fun-shaped structure; three spherical swellings at the base of semicells, with two additional swellings anteriorly (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Ushidome-ike (pond), Norikura highland, Azumi, Matsumoto city (formerly Azumi village), Nagano Pref., Japan, June 8, 2006 by Y. Tsukii