Genus: When extended, trumpet-shaped or cylindrical; highly contractile; some with mucilaginous lorica; conspicuous peristomal field frontal; contractile vacuole anterior-left; fresh water (Kudo, 1966).
Species: Colorless; with synbiotic Chlorella; 1-2 mm long when extended; macronucleus beaded; anterior end expanded (Kudo, 1966). Elongate, may attain 1-2 mm; peristome wide; macronucleus moniliform; no somatic bristles; colourless but zoochlorellae may be present (Carey, 1992).