Genus: One emergent flagellum; non-emergent flagellum ends within reservoir; colourless; osmotrophic; no eyespot; rigid; solitary; elongated; curved; strongly flattened (Illustrated Guide, 1985).
Species: Cell body banana-shaped, 64-100 μm long, 6-9 μm wide; bill-like rostrum, ventral line concave, dorsal line convex; a flagellum about a half of the body length (Angeler, Schagerl & Müller, 2002).