Choanocystis rossica  (Mikrjukov, 1995)
  
Diagnosis: Cells are 14–26 µm in diameter with plate-scales and one type of spicules in the periplast. Spicules are 3-7 µm long; the shaft is hollow, cylindrical, in the average, 0.5 µm thick in the base, is tapered in the direction of a cut off apex, which lacks marginal teeth; the base-plates is heart-shaped with straight edges. Plate-scales are from elliptical to elongated, in the average, 3.0 x 1.7 µm, flat, patternless, sometimes with more or less well-developed medial constriction.

Ecology: Freshwater. Russia, Estonia.