Genus Choanocystis Penard, 1904
Diagnosis: Centroheliozoa with a periplast with tangential plate-scales and radial spine-scales. The radial spine-scales have a cylindrical shaft, which inserts eccentrically at the apex of an invagination or incision of a heart-shaped base-plate.
Thirteen species, mostly freshwater.
References: Mikrjukov (1995b), Siemensma and Roijackers (1988a).
Type species: Choanocystis lepidula Penard, 1904