Phylum: Charophyta   Family: Desmidiaceae

Cosmarium pyramidatum subsp. abnorme J. Lütkemüller 1893

Kouwets (1987: 231, pl. 11: 11-12) described a population of pyramid-form cells, which were between C. pyramidatum and C. pseudopyramidatum in size and displayed three pyrenoids in most semicells. Krieger & Gerloff (1965: 121, pl. 25: 3) also described cells with three pyrenoids but with a large size-range suggesting more than one taxon is involved. Surprisingly, his drawing in side-view is remarkably quadrate? The population from the Wind Farm, South Uist was squeezed from Sphagnum and is similar in size to Kouwets' find with perhaps the isthmus measurements slightly broader. The pyrenoids are not always easy to see. Kouwets is proposing to raise this subspecies (his morpha) to species level [Cosmarium pyramidatiforme] but will not be accepted until published.
Cell dimensions: L: (58-)64-74 µm; B: 41-48 µm.; Is: 13-15.5 µm; Th: 28-31.5 µm; L/B: 1.45-1.56.
The status in the Outer Hebrides is unclear due to confusion over pyramidal-forms. It prefers acidic and oligotrophic habitats, occasionally with Sphagnum. It is also found in moorland pools and abandoned peat-cuttings.

References: 
Kouwets, F.A.C. (1987) Desmids from the Auvergne (France).
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium.
Krieger, W. & Gerloff, J. (1962-9) Die Gattung Cosmarium.
Lütkemüller, J. (1893) Desmidiaceen aus der Umgebung des Attersees in Oberösterreich.