Acanthocystis wiasemskii Ostroumoff, 1917
Diagnosis: Cells are 25-30 µm in diameter with plate-scales and one type of spicules in the periplast. Spicules are of the equal length, 12–15 µm, nail-shaped; the shaft is hollow, straight, 0.6 µm in diameter, of monotonous thickness, abruptly tapers on the apical end towards the pointed apex; the base-plate is rounded, about 2.5 µm in diameter. Plate-scales are about 4.0–5.0 x 2.0–2.5 µm, bean-shaped, with a fine granular apical surface.
Ecology: Marine. Black sea, Tasmanian Sea, marine aquaria in Moscow.