Genus (Perty, 1849): Oral cavity large, over most of ventrum; oral cilia as 1 long polykinetid (Illustrated Guide, 1985). Oval; dorsal side convex, ventral side concave; cytostome 3/4 to 4/5 the body length; on its left with a large membrane composed of may ciliary rows; contractile vacuole in mid-dorsal region; macronucleus ellipsoid, subterminal; a micronuleus; caudal cilia (Kudo, 1966). Species:

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No.2, Kannon-numa Forest Park (pond), Shimogo town, Fukushima Pref., Japan, November 15, 2008, by Y. Tsukii