Family & Genus: Test round, thick, firm, with rodlike radial structure (Illustrated Guide, 1985).
Genus: Thin test spherical to elongate ellipsoid; pseudostome terminal; many filopodia, branching and anastomosing; many species (Kudo, 1966).
Gromia oviformis Dujardin, 1835: Cell body 150 - 3000 μm diam.; test round to elliptical; pseudostome 1/5 diam of test, with short collar, membranous, clear; pseudopods faintly granuluated, branching, anastomosing; multinucleated (Illustrated guide, 1985).
Gromia fluvials: Cell body 90 - 250 μm diam.; test spherical, smooth, membranous and slightly flexible, or with sparsely distributed siliceous particles; filopodia (pseudopods) anastomosing; cytoplasm yellowish; fresh water (How to know the protozoa, 1979).