Genus: Solitary or colonial; body surface delicate; one to two chloroplasts; usually with a stigma; fresh water (Kudo, 1966). One to several chloroplasts; pyrenoid and/or eyespot (stigma) in some; cells naked, globular, ellipsoidal or pyriform (Illustrated Guide, 1985). Species:

31 μm 63 μm 94 μm; x 640

M. guttula Ehrenberg: Spherical to ovoid; 14-16 μm long; free-swimming or attached; longer flagellum about one to two times body length; cysts 12 μm diam. (Kudo, 1966).

M. elongata Stokes: Elongate; about 11 μm long; anterior end obliquely truncate (Kudo, 1966).

M. socialis Kent: Spherical; 5-10 μm long (Kudo, 1966).