Genus: Test ovoid, symmetrical, compressed, composed of a transparent membrane with or without adherent extraneous particles (Cash & Wailes, The British Freshwater Rhizopoda and Heliozoa vol. III, 1915). Species: Test covered with many grains of quartz and various extraneous particles, 55-97 μm long, 31-74 μm wide; pseudostome lacking any collar, cytoplasm containing algal endosymbionts (Cash & Wailes, The British Freshwater Rhizopoda and Heliozoa vol. III, 1915).

31 μm 63 μm 94 μm; x 640

Amphitrema stenostoma Nüsslin, test 95 μm long, 63 μm wide, L/W=1.5, cell body 58 μm long, 40 μm wide, L/W=1.5, x 640, a small marsh near prefectural road route 342, Sukawa highland, Kurikoma mountain, Higashi-naruse village, Akita Pref., Japan, June 24, 2007 by Y. Tsukii
31 μm 63 μm 94 μm; x 640

Test 75 μm long, 58 μm wide, L/W=1.3, cell body 50 μm long, 40 μm wide, L/W=1.3, x 640

Images of collecting locality: a small marsh near prefectural road route 342, Sukawa highland, Kurikoma mountain, Higashi-naruse village, Akita Pref., Japan, June 24, 2007 by Y. Tsukii