Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus corniculatus var. spinigerus (W. West) H.T. Croasdale 1957

First described and illustrated by West (1892: 171, pl. 22: 12) as Staurastrum corniculatum var. spinigerum. It was much later transferred to the current genus by Croasdale (1957: 124). It differs from the nominate in its smaller size and supporting short spines at the apical angles. In their later flora, West & West (1912: 164) note under the nominate variety: “St. corniculatum is a very rare Desmid. But the following variety [spinigerum], although rare, appears to be widely distributed.”
Cell dimensions: L: 23-30 µm; B: 17-26 µm.; Is: 9-13 µm; Sp: 2-4.
A rare species found in slightly acidic waters, usually in the plankton of mesotrophic shallow lochs. It would appear to have an Atlantic distribution.

References: 
Croasdale, H.T. (1957). Freshwater algae of Alaska I. Some Desmids from the Interior. Part 3 Cosmariae concluded.
West, W. (1892). A contribution to the freshwater algae of west Ireland.
West, W. & West, G.S. (1912).. A Monograph of the British Desmidiaceae, Volume 4.