Family: Cirral files spiral obliquely around body. Genus: Slender or ovoid or fusiform; usually 4 spiral rows of crri; sometimes tube-dwelling (Kudo, 1966). Body long with pointed anterior; loricate; posterior of body blunt, round (Illustrated Guide, 1985). S. gracilis posterior end pointed (Carey, 1992). Species: 130-200 μm long; fresh water (Kudo, 1966).

100 μm 200 μm 300 μm; x 200

Images of collecting locality: Tatsumi-ike (a pond), Tatsumi park, Nagano city, Nagano Pref., October 19, 2008, by Y. Tsukii