Body filiform when fully extended, anterior and posterior portions tapering, glabrous stripe wide, head claviform, oral bulge inconspicuous, brosse cleft indistinct; highly flexible, contractile, flattened. Contracted specimens banana-shaped, glabrous stripe distinctly protruding on convex side. Nuclear capsule single, ellipsoidal, 15-30 µm long, composed of 4-18, often 12, macronuclei and 2-8, usually 6, micronuclei. No contractile vacuole. Cortical granules minute, yellowish, between ciliary rows and in glabrous stripe. Somatic kineties 19-27 in number, composed of dikinetids; nonciliated glabrous stripe enclosed by bristle kinety, which consists of quite irregularly arranged dikinetids with rather stiff cilia. Circumoral kinety of dikinetids interrupted at brosse cleft; 2-4, commonly 3 short oblique brosse kineties. Movement gliding and winding. Size in vivo 1000-1500 x 30-50 µm, fully contracted specimens about 600 µm. Usually a mesopsammal species which has several synonyms and homonyms (Raikov, 1962).
Ref.: Kahl (1927), Raikov (1962), Raikov and Kovaleva (1994), Foissner and Dragesco (1996b).