(Müller, 1773)
Ehrenberg, 1830
Body broadly elliptical to slightly triangular; 7-9 distinct longitudinal dorsal ribs. Oral cavity large, V-shaped; lip on right border extends almost to posterior pole. Macronucleus horseshoe-shaped, 1 micronucleus. One contractile vacuole. Ten frontoventral, 4-6 (usually 5) transverse, 2 left marginal and 2-6 caudal cirri. Dorsal kineties 9-12 in number, with 10-40 cilia in central rows. Adoral zone extends arch-like over 2/3-4/5 of body length, composed of 51-70 membranelles. Dorsal silverline system of double-eurystomus type. Size 70-110 x 50-100 µm.
Ref.: Kahl (1932), Tuffrau (1960), Borror (1968), Curds (1975), Song and Packroff (1997).