Phylum: Charophyta   Family: Desmidiaceae

Xanthidium antilopaeum f. dimazum (Nordstedt) Petlovany 2015

This rare form is only distinguished from the nominate variety by the presence of a curved row of granules near the apex of the semicells. Nordstedt (1873, p. 38, pl. 1: 20 [as var. dimazum]) first described it from Norway. Petlovany [In Tsarenko, Wasser & Nevo (editors) (2014, p. 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, p. 63) make no mention of it.

References: 
Coesel, P.F.M. & Meesters, K.J. (2007) Mesotaeniaceae and Desmidiaceae of the European 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.