Lorica highly variable, slenderly to broadly triangular, anteriorly transversely truncate, usually occupied by entire cell; distinctly flattened; transversely striated in some populations (different species?). Two bundles of tentacles inserted on hemispherical papillae on apical ends of cell projecting through openings on opposite sides of lorica, each bundle consisting of 4-30 (often 10-20) tentacles, up to 80 µm long, with globular ends. No articulation between lorica and stalk, which may be very short to 5 times lorica length (2-5 µm wide). Macronucleus globular to ellipsoid, several micronuclei. One contractile vacuole in anterior body half. Lorica 23-200, usually 40-100 x 25-80 µm. Swarmer ellipsoidal, in vivo 35 x 25-30 µm, with 7 long and 1 short oblique ciliary rows which are ventrally interrupted.
Ref.: Kahl (1934), Curds (1985), Matthes et al. (1988), Foissner et al. (1995).