Genus: Cell body oblong or fusiform; peristome conspicuous, beginning at the anterior end and reaching the middle of the body; contractile vacuole terminal; macronucelus ovoid to elongate; fresh or salt water; sapropelic, some parasitic; many species (Kudo, 1966). Cell body asymmetrical and elongate, anterior twisted to the left, band-like AZM twisted round and down the body (Carey, 1992). Species: Cell body 120-200 μm long; saporpelic (Kudo, 1966). Cell body elongate, reduced in width posteriorly, 160 μm long, anterior large and twisted to the left, projecting some distance from the body, AZM curves down to the eqauatiorial region, posterior reduced in width with blunt end, no caudal cilia, a single ovoid macronucleus, a single terminal contractile vacuole (Carey, 1992).

50 μm 100 μm 150 μm; x 400

31 μm 63 μm 94 μm; x 640

M. es (Claparède and Lachmann, 1858) Kahl, 1930-5: (Syn. Metopus sigmoides Claparède and Lachmann, 1858 ) Cell body elongate, 160 μm long, anterior large and twisted to the left, slightly protruded from the body, AZM curving down to the equatorial region, posterior narrowed with a blunt end, no caudal cilia, a single macronucleus ovoid, a single contractile vacuole terminal (Carey, 1992).