Genus: Free-living; skeleton with or without coat; cuirass made of scales and of the basal part of the spicules; coat indistinguishable (Illustrated Guide, 1985). Siliceous scales arranged tangentially and radiating siliceous spines with pointed or bifurcated ends; (Kudo, 1966). Species: Tangential scales stut and pointed; spines curved and nail-headed; a single contractile vacuole; diameter 35-40 μm; spines about 1/3 the body diameter (Kudo, 1966).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: No. 2, Oyumi-ike (a pond), Chuo-ku, Chiba City, Chiba Pref., Japan, December 24, 2007 by Y. Tsukii