Body cylindrical to bottle-shaped, neck not distinctly elongate; highly contractile, pellicle usually appears annulated (from slight contraction?). Macronucleus elongate ellipsoidal. Contractile vacuole with collecting canals in posterior end. About 48 somatic kineties. Conspicuous extrusomes (ca. 30 µm long) and elongate cilia surround apical oral aperture. Size in vivo 150-350 x 70-100 µm. Encysts readily on slide; resting cysts bottle-shaped. Usually a mesopsammal species (Dragesco, 1960) but also found on copepods (Hamburger and Buddenbrock, 1911). Redescription necessary.
Ref.: Hamburger and Buddenbrock (1911), Kahl (1930), Dragesco (1960).