Genus (Ehrenberg, 1830): Spheroidal; cytoplasm vacuolated, especially ectoplasm; nucleus central; one to many contractile vacuoles; axopodia straight, axial filaments terminate at surface of the nucleus (Kudo, 1966). Species: Ectoplasm vacuolated; a large central nucleus; diameter average 40-50 μm (Kudo, 1966).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: A small dam at Ichinokawa (river) near Suwa-numa, Minami-yoshimi, Yoshimi town, Saitama Pref., Japan, March 25, 2006 by Y. Tsukii