Phylum: Charophyta   Family: Desmidiaceae

Micrasterias fimbriata Ralfs 1848

A rare desmid found in oligo-mesotrophic waters. 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, p. 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).

References: 
Ralfs, J. (1848) The British Desmidieae.
West, W. & West, G.S. (1905) A Monograph of the British Desmidiaceae, Volume 2.
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European Lowlands.