Genus: Biflagellate, both arising from anterior end; one directed anteriorly and the other runs backward over body surface as a trailing (recurrent) flagellum; body plastic (Kudo, 1966). Small (10-15 μm); body is generally pyriform to cylindrical except for an ameboid variable posterior (Illustrated Guide, 1985). Species:

31 μm 63 μm 94 μm; x 640

Cercomonas longicauda Dujardin: Cell body pyriform or ovoid, 18-36 μm long, 9-14 μm wide; posterior end drawn out; flagella as long as body; pseudopodia present; fresh water and coprozoic (Kudo, 1966).

Cercomonas crassicauda Dujardin: Cell body 10-16 μm long, 7-10 μm wide; fresh water and coprozoic (Kudo, 1966).