Genus Hedriocystis Hertwig & Lesser, 1874
Diagnosis: Cell surrounded by a non-silicious stalked shell; shell hyaline, colorless, with small holes, pores, through which non-branching axopodia radiate; stalk not always distinct, at one species never observed; central nucleus; Schwärmer observed at two species, with one or two flagella.
Type species: Hedriocystis pellucida
Key to the species
|1||Stalk longer than the test||
|–||Stalk shorter than the test|
|2||Shell polygonal and/or with clear conical nipples|
|–||Shell circular or ovoid in circumference|