Choanocystis Penard 1904

Centroheliozoa with a periplast with internal tangential plate-scales and external radial spicules. The radial spicules have a cylindrical shaft, which inserts eccentrically at the apex of an invagination of a heart-shaped base-plate. Thirteen species, mostly freshwater, type-species - C. lepidula Penard, 1904

Centroheliozoa with a periplast comprising three types of scales: straight tubular or trumpet-like radial scales, smaller funnel-shaped radial scales, and tangential elliptical plate-scales. The plate scales have a broad, hollow marginal rim, a smooth or reticular central area and a well-developed or vestigial medial rib as in Polyplacocystis. Type species: R. lemani (Penard, 1891) Penard, 1904.