Genus: Only 1 emergent flagellum; locomotory flagellum directed anteriorly, straight, during swimming; colourless, phagotrophic; no eyespot; rigid, solitary, ovoid, usually flat, with several keels; freshwater (Illustrated Guide, 1985). Oval or pyriform; not plastic; pellicle often with straight or spiral furrow; a single flagellum; many species (Kudo, 1966).
Species: 30-35 μm; 2 dorsal, 2 ventral grooves on either side of dorsal and ventral keels (How to know the protozoa, 1979).