Family: Test round, thin, firm to elastic, some with spines or spicules (Illustrated Guide, 1985).
Genus: Test consisting of a thin, flexible, homogeneous envelope, colorless or translucent, without adherent paticles; pseudostome terminal, elastic; cytoplasm colorless, granular, completely filling the test; nucleus large, placed posteriorly; pseudopodia numerous, long, branching but not anastomosing (Cash & Wailes, 1915). Pseudostome oval, cells clustered (Illustrated Guide, 1985).

Lecythium sp. 3 clips test 16 μm Japan, 1998