Genus: Emergent flagellum mobile throughout its length during swimming; colourless; no eyespot; cell body rigid; cylindrical, not flattened; canal opening subapical; paramylon and lipid abundant; fresh water (Illustrated Guide, 1985). Body rigid, cylindrical, more or less arched; pellicle longitudinally ridged; a flagellum at apex (Kudo, 1966).
Species: Banana-shaped; longitudinal ridges; flagellum as long as cell body; 15-25 μm long, 7-8 μm wide (Hall, 1923), 13-15 μm long, 5-7 μm wide (Hollande, 1952); standing water (Kudo, 1966).