Genus Hyalodiscus Hertwig & Lesser, 1874

Diagnosis: Cells discoid with breadth greater than length. Extensive, flattened hyaline margin surrounding the cytoplasmic hump anteriorly and laterally and sometimes posteriorly. Locomotion frequently rapid with a distinctive rolling motion. Fine, short subpseudopodia extend from the hyaloplasm. Floating form with radiate pseudopodia. Cytoplasmic mass sometimes reddish brown or greenish in color with 1 or 2 nuclei.
At least 4 described species from freshwater and marine habitats.
Type species: Hyalodiscus rubicundus Hertwig & Lesser,  1874