Family: Test rigid, chitinoid, oval to flask-shaped, clear; pseudostome terminal (Illustrated Guide, 1985).
Genus: Test ovate, discoid in cross-section; pseudostome a terminal slit (Illustrated Guide, 1985).

H. papilio 4 clips test 56 x 37 μm Torinome Kuriso Tochigi, 1999

Hyalosphenia sp. 3 clips Numabe Yamagata Yamagata, 1999

H. papilio 4 clips Shirasaka Shirakawa Fukushima, 1999