Genus: Postoral kineties usually to left of oral poykinetids (Illustrated Guide, 1985). Left edge is more curved than right edge; cytopharynx with numerous strong fibrils; ectoplasm with numerous fusiform trichocysts; macronucleus oval; one to several micronulei (Kudo, 1966). Species: 150-600 μm long; ventrally flattened; dark colored; buccal cavity close to anterior end (How to know the protozoa, 1979). Elongate 150-600 μm long; anterior is not wider than posterior; cytostome small with well defined pre- and postoral suture; a large macronucleus with three micronuclei; single contractile vacuole with 12 radiating canals; many trichocysts (Carey, 1992). Cell body 150-600 μm long (Kahl, 1930).

100 μm 200 μm 300 μm; x 200

Frontonia sp.,isolated macronuclei, 125-138 μm long, x 200, by Y. Tsukii