Family: Pseudostome terminal, of variable shape.
Genus: Pseudostome lacks lobed collar; test round or oval in cross-section; pseudostome relatively large, with or lacking a collar (Illustrated Guide, 1985).
Species: 45-50 μm long for small varieties, 100-600 μm long for large varieties; 25-30 μm wide (test diam.), small; 70-350 μm wide, large; test flask-shaped, base round or polygonal, narrow tapered neck; chitinoid, large imbedded quartz grains; Symbiont, green alga (Kudo, 1966).