Genus: Small, ovoid, but plastic; cytostome anterior; encystment common (Kudo, 1966).
Cytostome at the tip of a short rostrum which is ventral or tateral to the flagellar pocket
(Illustrated Guide, 1985).
B. caudatus Dujardin: Highly flattened; usually tapering posteriorly; 11-22 μm long, 5-10 μm wide; anterior flagellum about body length; trailing (recurrent) flagellum longer; blepharoplast (Kudo, 1966).
B. edax Klebs: Pyriform with bluntly pointed ends; 11-15 μm long, 5-7 μm wide (Kudo, 1966). Ovoid; common in stagnant waters and plast infusions (How to know the protozoa, 1979).