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

Images of collecting locality: a small waterway at walking road along Kurome river, Kanayama-machi, Higashikurume city, Tokyo, Japan, April 20, 2008 by Y. Tsukii