Phylum: Charophyta Family: Desmidiaceae
Cosmarium subtumidiforme F.A.C. Kouwets
This is a proposed new name for a species only previously known from a moorland pool in the Netherlands. It will have no authenticity until published but I will leave it here for reference. The author has confirmed my find which is a first British record. He comments "The taxonomy of smaller, smooth-walled Cosmarium forms is very much confused. Force fitting and taxonomic drift has obscured a clear species concept."
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium