Phylum: Charophyta   Family: Desmidiaceae

Cosmarium neocrenatum Van Westen & Coesel 2021

It has much in common with the confused species complex of Cosmarium crenatum Ralfs (1848: p. 96, pl. 15: 7a-c). When Ralfs described this species, he made no mention of central ornamentation. Nordstedt (1872, p. 30, pl. 6: 7) described a number of larger forms with various central ornamentation. The authors decided that these broader forms warranted species status. The central ornamentation can be quite ephemeral and deep focus is often needed to see it. The Stornoway samples show 5-6 supraisthmial granules and up to five elongated warts.

References: 
Van Westen, M.C. & Coesel, P.F.M. (2021) Taxonomic notes on desmids from the Netherlands IV, with a description of another five new species.
Ralfs, J. (1848) The British Desmidieae.
Nordstedt, O. (1872) Desmidiaceae ex insulis Spetsbergensibus et Beeren Eiland in expeditionibus annorum 1868 et 1870 suecanis collectae.
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium.