(Claparède and Lachmann, 1859)
Body roughly ellipsoidal, anteriorly obliquely truncate; ventral plate distinctly smaller than dorsal plate. Dorsoventrally slightly flattened. Stylus usually inconspicuous, distinctly subterminal on right ventral side. Two contractile vacuoles. Oral basket wide, composed of many nematodesmal rods which lack a prominent tooth. Cytoplasm often dark red (from food?). Pigment spot on anterior left of body. Right ciliary field rather wide. Movement slowly gliding. Size in vivo 80-140 x 40-70 µm. Third contractile vacuole found by de Morgan (1925) is very likely an artifact.
Ref.: Hamburger and Buddenbrock (1911), Kahl (1931), Deroux and Dragesco (1968), Deroux (1974).