Phylum: Charophyta   Family: Desmidiaceae

Cosmarium notabile L.A. de Brébisson 1856

De Brébisson’s original description and accompanying figure are poor, which has led to possible misidentifications. Van Geest & Coesel (2019) found cells in ephemeral rainwater puddles near Amsterdam, which they feel fits De Brébisson’s original description; it is their concept that is followed here. Several of these granulate species show a degree of morphological variability making them sometimes difficult to identify. It needs to be compared with Cosmarium neonotabile Van Westen & Coesel 2021, but that species is smaller with little or no overlap in cell dimensions.
Cell dimensions: L: 30.1-33.2 µm; B: 23.7-24.5 µm; Is: 13.7-14.8 µm; Th: 16.2-18.1 µm; L/B: 1.27-137.
In view of the foregoing, distribution is largely unknown. It does seem to be a rare desmid confined to ephemeral pools and mosses on wet rocks.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.
Van Geest, A. & Coesel, P. (2019). Some new and interesting desmids (Streptophyta, Desmidiales) from ephemeral puddles in the urban and industrial areas of Amsterdam (Netherlands).