Body barrel-shaped to globular, with anterior oral cone. Macronucleus single, sausage-shaped. Terminal contractile vacuole very likely. Extrusomes (cyrtocysts) rod-like, scattered in body, in protargol slides often curved; other extrusomes (developmental stages, pexicysts?) fusiform, 4-6 µm long. Toxicysts 40-50 µm long, between 25-50 µm long nematodesmata. Basal body rows 50-75 in number extending from posterior pole almost to oral cone, usually nonciliferous except 2 ciliary wreaths (1 at anterior end of somatic kineties, 1 in rear 1/4 of body, about 15 cilia wide) and dorsal brush (posterior to each ciliary wreath, composed of 2-3 short rows of paired basal bodies). Swims moderately fast. Size in vivo 70-200 x 50-120 µm.
Ref.: Meunier (1910), Petz et al. (1995a).