Phylum: Charophyta   Family: Desmidiaceae

Cosmarium tetraophthalmum Brébisson ex Ralfs 1848

Ralfs (1848, p.98, pl.17:11) accredited authorship of this taxon to Kützing (1833, p.597, pl.19:87) who named it Heterocarpella tetrophthalma but as this predates the start of desmid nomenclature, it has no authenticity. Kützing’s rather small drawings show the sinuses gaping. Ralfs moved this taxon to the genus Cosmarium and, interestingly, replicated the gaping sinuses in Edward Jenner’s drawings. West & West (1908, p.270, pl.95:4-7) note 'Very common in the Outer Hebrides... is found generally distributed over the whole of the British Islands, but more especially in Sphagnum-bogs and in peaty moorland ditches'. They question the granulation size and pattern as noted by Ralfs, and later authors have made similar comments. It has become clear that more than one taxon is being discussed and the cells with smaller and more numerous granules belong to a different taxon. This has been provisionally names Cosmarium tetraophthalmum L.A. de Brébisson ex J. Ralfs 1848, sensu auct. Nonnull.

References: 
Kützing, F.T. (1833) Synopsis diatomearum oder Versuch einer systematischen Zusammenstellung der Diatomeen.
Ralfs, J. (1848) The British Desmidieae.
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3.
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium.