Genus: Body ellipsoid; anterior end truncate; posterior end rounded; peristome wide and V-shaped; a large membrane on right edge and adoral zone on left; macronucleus moniliform (Kudo, 1966). Species: Cell body ovoid, 180 μm long, anterior truncated, peristome wide triangular, posterior rounded with a slight bump terminal, three large macronuclei, no contractile vacuole ?, kineties spiral (Carey, 1992).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

C. vastum Bock, 1955: Cell body ovoid, 180 μm long, anterior truncated, peristome wide triangular, posterior rounded with a slight bump terminal, three large macronuclei, no contractile vacuole ?, kineties spiral (Carey, 1992).

C. nigra Dragesco, 1960: cell body small, ovoid, rounded at both ends, 300 μm long, peristome small, but undulating membrane large, macronucleus moniliform, contractile vauoles along both edges of the body, dark blue mucocysts present (Carey, 1992).