Family:
Genus: Body ovoid, inflexible; ventral surface flattened, dorsal surface convex; peristome broadly triangular (Kudo, 1966). Cell body is ovoid, dorsoventrally flattened; dorsal surface may be equipped with some ornamentation; three groups of cirri (frontoventral, transverse & caudal); macronucleus C-shaped, "3"-shaped, or horsehoe-shaped (Carey, 1992).