Members of this family have 1 long and 1 short flagellum.
The body is active and plastic. Chromatophores are absent. This genus is the colorless homolog of Ochromonas. Reynolds (1934) recognized 13 free-living species, and in addition there is at least 1 coprophilic one.
Noble (1956) cultivated Monas sp. in bovine feces at 4 C° in the refrigerator for 5 months. He also (1958) found that Monas sp. appeared in fecal samples from Wyoming elk, bison and bear after storage at 4 C° for 7 to 27 days. The protozoa persisted for several weeks and then died out. They failed to survive in soil or in soil mixed with boiled feces, nor could they be found in soil samples taken from areas where elk, sheep or horses were present. Noble concluded that this and other coprophilic protozoa may require certain essential metabolites produced by bacteria. The form which Noble studied was spherical and 4 u in diameter. He assigned it to the "Monas communis" reported by Becker and Talbott (1927) from the rumen of cattle, but the latter had only a single flagellum and was Sphaeromonas communis.
Monas obliqua Schewiakoff has been found in material from bulls submitted for Tritrichomonas foetus diagnosis (Morgan and Hawkins, 1952).
In this order the chromatophores, if present, are green. The stored reserves include lipids and paramylum. There is a reservoir or "gullet" from the posterior or postero-dorsal wall of which the flagella arise. There are 3 suborders in the Euglenorida, of which the Euglenorina includes one genus containing coprophilic forms.