Phylum: Charophyta   Family: Desmidiaceae

Micrasterias fimbriata J. Ralfs 1848

First described and illustrated by Ralfs (1848: 71, pl. 8: 2). Similar to Micrasterias apicula but that species has a more ornamented polar lobe and more spines on the surface in face-view. West & West (1905: 99, pl. 47: 3-4 [as M. apicula var. fibriata]) show a figure (l.c., pl. 46: 6) of an exaggerated curved polar spine very similar to the one found at Eisgein (see image below).
Cell dimensions: L: 200-280 µm; B: 170-240 µm; Is: 30-37 µm; L/B: 1.05-1.20.
A rare desmid found in oligo-mesotrophic waters.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Ralfs, J. (1848). The British Desmidieae.
West, W. & West, G.S. (1905). A Monograph of the British Desmidiaceae, Volume 2.