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: Large, ovoid, 120-200 μm long; oral aperture (cytostome) extends almost to the posterior of the cell; a tuft of caudal cilia posterior; contractile vacuole dorsal; macronucleus ovoid and curved (Carey, 1992). 120-200 μm long; posterior cilia 40-50 μm long (Kudo, 1966). Body elliptical; long cytostome 3/4 body length; with large undulatory membrane on left oral margin; macronucleus kidney-shaped, near rear end; fresh water (How to know the protozoa, 1979).