Genus: Ovoid; ciliation uniform; long stiff cilia (bristles) distributed over the body surface; peristome deep, both anterior and posterior regions with a well-developed membranes connected with undulating membrane (velum); two macronucleus; 1-2 micronuclei; several contractile vacuoles; fresh water (Kudo, 1966). Species:

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

Histiobalantium (natans or marinum or a similar species), cell body fattened with coverglass, small trichocysts visible, x 640, Doman-green Park, Nishi-Urawa, Saitama Pref., Japan, February 2003 by Y. Tsukii

Histiobalantium natans (Claparède & Lachmann): 70-110 μm long (Kudo, 1966).

Histiobalantium marinum Kahl, 1933: Reniform; oral area large, located centrally; 80 μm long (Carey, 1992).

Histiobalantium semisetatum Noland: Elongate ellipsoid; posterior end bluntly rounded; a single macronucleus spherical; longer cilia (bristles) on posterior half only; contractile vacuole on dorsal side; 126-205 μm long; salt water (Kudo, 1966).

Histiobalantium majus Kahl, 1931: Reniform, with a bluntly pointed posterior; oral area large; many trichocysts; 150 μm long (Carey, 1992).