Body lanceolate, posteriorly narrowed tail-like; flexible, contracts without torsion (about 50% of body length). Macronucleus moniliform, composed of about 7-27 nodules. Very likely with several micronuclei. Contractile vacuole in posterior end. Cortical granules between kineties, specimens thus perhaps reddish. Somatic kineties 32-38 in number. Adoral zone extending along 1/3-1/4 of body, composed of about 150 membranelles; cytostome invaginated. Undulating membrane inconspicuous, fragmented, composed of about 40 short rows of 3-5 cilia. Thigmotactic, attaches to substrate with posterior portion. Swims in helical lines. Size 200-1100 x 15-55 µm. There are several rather similar species which differ only in the shape of the undulating membrane (Dragesco and Dragesco-Kérneis, 1986).
Ref.: Kahl (1932), Borror (1963), Dragesco and Dragesco-Kérneis (1986).