Family: Apical cytostome eccentric, oral dikinetids along extended flailing anterior end ("proboscis");
toxicysts on ventrum of proboscis.
Genus: Body long, rear usually pointed (Illustrated Guide, 1985). Elogate; snout or neck-like prolongation (proboscis) conspicuous; contractile vacuoles two or more (Kudo, 1966). Contractile vacuoles usually lie in a row along the dorsal surface (Carey, 1992).