Hyalosphenia penardi Lauterborn, 1908

Diagnosis: Shell transparent, colorless, yellow or brown, elliptical with a strongly curved, nearly semi-circular pseudostome; fundus broadly rounded; surface without structure; plasma usually partly filling the shell, with some epipodia; shell strongly compressed, especially towards the aperture; nucleus globular with a number of spherical nucleoli.

Dimensions: According to Lauterbornd (1908): Shell length 180 µm, width 70 µm.

Ecology and distribution. Freshwater, among diatoms. Food: mainly diatoms.

Geographical distribution: Upper Rhine in Germany, by Lauterborn, and, unless it is a new species, in a canal in IJburg, Amsterdam, the Netherlands, by Cagri Yalcin (catched in his plankton net).

Remarks: This species was (probably) rediscovered in the Netherlands in 2021 by Cagri Yalcin who published the video below on YouTube.  Probably, as it could also be a new species, as there is a narrowing, a kind of neck, above the aperture and the shell is clearly dotted.