Genus: Pseudostome lacks lobed collar; test round or oval in cross-section; 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).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: a pond near the entrance of climbing route to Omine mountain, Minakami town (formerly Tsukiyono town), Gunma Pref., Japan, May 25, 2006 by Y. Tsukii