Family: Small sized; few body cilia; distinct caudal cilium; paroral dikinetid rarely extends forward and left of cytostome (Illustrated Guide, 1985).
Genus: Small, 15-60 μm long; with a caudal cilium; on the right edge of peristome occurs a membrane which forms a pocket around cytostomal groove; contractile vacuole posterior (Kudo, 1966). Ovoid body with flattened anterior cap; long peristome with large, undulatory membrane, extended in feeding, one long caudal cilium (How to know the protozoa, 1979). No somatic cilia at the anterior apex; no cilia around the posterior where a single, long caudal cilium usually merges; buccal ciliature proportionally smaller in comparison to Pleuronema (Carey, 1992).