Genus: Pseudostome lacks lobed collar; test round or oval in cross-section; pseudostome relatively large, with or lacking a collar (Illustrated Guide, 1985). Species: Test pyriform, flask-shaped, or ovoid; neck variable in length; aperture terminal, typically circular; test composed of angular sand-grains, diatoms; 60-580 μm by 40-240 μm (Kudo, 1966).