Hedriocystis minor Siemensma, 1991
Diagnosis: Shell spherical or ovoid, smooth, tapering towards the stalk; some small pores; shell hyaline, colorless or faint yellow; cell body doesn’t fill the shell completely; nucleus subcentrally; one contractile vacuole; axopodia not numerous, fine; no swarmer observed.
Dimensions: shell 8-13 µm, stalk up to 30 µm long.
Ecology: fresh water, on submerged waterplants, Sphagnum; the Netherlands, Austria.
Remarks: rare, but easily overlooked, because of its small size.