The Genus PetalomonasStein 1878

Stein, F. R.: Der Organismus der Infusionstiere. III. Abt. Der Organismus der Flagellaten. -Leipzig 1878.

Lee, John J., Hunter, Seymour H., & Bovee, Eugene C. (eds) An illustrated Guide to the Protozoa The Society of Protozoologists. 1985.

Diagnosis:

Only 1 emergent flagellum; a 2nd (non-emergent flagellum) not recorded but presumably present (see Leedale, 1967a); locomotory flagellum directed anteriorly, straight, during swimming; colourless, phagotrophic, ingestion organelle recorded by one author but denied by all others; no eyespot; rigid, solitary, ovoid, usually flat, with several keels; canal opening subapical; many species, freshwater. See Shawhan & Jahn (1947), Christen (1967). Related genera with one emergent flagellum are Atraktomonas Christen, with rigid fusiform unflattened cell, and the phagotrophic Calycimonas Christen, with rigid ovoid unflattened cell. (from Illustrated Guide)