Phylum: Charophyta   Family: Desmidiaceae

Xanthidium polymazum (C.F.O. Nordstedt) P.F.M. Coesel & K.J. Meesters 2023

First described and illustrated by Nordstedt (1873: 38, fig. 10) as a variety of Xanthidium antilopaeum. Recently, Coesel & Meesters (2023: 195) raised it to species level. This rare form is distinguished by the presence of a curved row of granules near the apex of the semicells.
Cell dimensions: L: 46-68 µm; B: 45-62 µm; Is: 16-18 µm; Sp: 13-15 µm; Overall LxB: 62-85 x 58-80 µm.
Petlovany [In Tsarenko, Wasser & Nevo (editors) (2014: 443)] gives few European sites, confined to the northern countries. He notes the habitat as "benthic in bogs, peatbogs and lakes; oligotrophic." West & West (1912) make no mention of it.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Nordstedt, C.F.O. (1873). Bidrag till kännedomen om sydligare Norges Desmidiéer.
Tsarenko, P.M., Wasser, S.P. & Nevo, E. (editors) (2014). Algae of Ukraine, Volume 4: Charophyta.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.