Description of Polyplacocystis

Centroheliozoa with a periplast comprising one or several types of tangential spindle-shaped or flat siliceous scales which have a reticular or smooth upper surface and a hollow marginal rim. There are no internal septae. Radial elements absent. Five species from marine and freshwater habitats, type species, P. symmetrica (Penard, 1904) Mikrjukov, 1996, is from freshwater.