166 BRITISH DESMIDIACEJE. 



WALES. Fairly general in Carnarvonshire and 

 Merioneth ! 



SCOTLAND.- -Sutherland !, Inverness, Aberdeen, Kin- 

 cardine, Forfar !, Perth ! (Boy $ Bissett). At 3,500ft. 

 on Lochnagar, Aberdeen ! Not uncommon in the 

 plankton ! Outer Hebrides ! Orkneys ! Shetlands ! 



IRELAND.- -Donegal ! Mayo ! G-alway ! Kerry ! Dub- 

 lin and Wicklow (Archer). Londonderry ! Down ! 

 Armagh ! 



Geogr. Distribution. France. Germany. Austria 

 and Galicia. Poland. Hungary. Italy. Bosnia. 

 Finland. Norway. Sweden. S. Russia. Siberia. 

 Greenland. Spitzbergen. Nova Zembla. Central 

 China. New Zealand (var.). Central Africa. Azores. 

 United States. 



C. bioculatum is one of the most generally distributed of 

 the small, smooth species of the genus. It is distinguished at 

 once from all its allies by the spiny zygospore. The spines 

 are stout, very blunt,, and not very numerous,, from nine to 

 eleven being visible around the periphery of the spore. 



The semicells are somewhat narrowly elliptic or elliptic- 

 oblong-, and the sinus is slightly open. 



Forma depressa Schaarschm. (PI. LXI, figs. 8, 9.) 



C. bioculatum Breb. forma depressa Schaarschm. Magyar. Desni. 1883, 

 p. 270, t. 1, f . 10 ; De Toni, Syll. Alg. 1889, p. 934 ; West, Alg. Eng. 

 Lake Distr. 1892, p. 725 ; Alg. S. England, 1897, p. 486. 



Cells subquadrate, with rounded angles, sinus open ; 

 semicells transversely oblong with broadly flattened 

 apices; vertical view oblong, sides parallel and poles 

 rounded. 



Length 14*5-20 p.; breadth 17-18 p.. 



ENGLAND.- -Brother's Water, Westmoreland ! Epping 

 Forest, Essex ! Keston Common, Kent ! 



Geofjr. Distribution. Galicia in Austria. Hungary. 

 Kew Zealand. 



Var. hians West & G. S. West. (PI. LXI, figs. 10, 11.) 



C. Uoculatum Breb. var. hians West & G. S. West, Alg. S. England, 1897, 

 p. 486, t. 6, f. 24. 



