Genus: Highly flattened; pellicle firm; body form constant (Kudo, 1966). Chloroplasts small, discoid, pyrenoids usually absent; most species flat and leaf-shaped; often with ridges or fins running helically or longitudinally (Illustrated Guide, 1985). Species: 40-55 μm long, 32-40 μm wide; a short caudal projection; pellicle with minute knobs arranged in longitudinal rows; flagellum about the body length (Kudo, 1966). 43-54 μm long; pointed rear; incurved anteriorly with small papilla; striated, about 12 rows of small knobs; fresh water (How to know the protozoa, 1979).