/4 BRITISH DESMIDIACE^. 



Length 26-5-48 //,; breadth 20-39 //,; breadth of 

 apex 19-26 jn; breadth of isthmus 5 "2-1 2*5 //,; thick- 

 ness 18-21 /x. 



ENGLAND.- -Borrowdale and Scarf Gap Pass, Cumber- 

 land! Westmoreland! (Rolfs). Ogden Clongh, Peny- 

 ghent, Oughtershaw Tarn, and Cautley Spout, W. 

 Yorks ! 



WALES. Bettws-y-coed, Twll Du, and Llyn Teyrn on 

 Snowdon, Carnarvonshire! Dolgelly, Merioneth (Ralfs). 



SCOTLAND. Sutherland !, Ross, Inverness, Aberdeen, 

 Kincardine, Forfar, Perth, Argyll (Roy fy Bissett). 



IRELAND.- -Lough Fea, Londonderry! Dublin and 

 Wicklow (Archer). 



Geogr. Distribution. France. Germany. Galicia 

 and Austria. Hungary. Italy. Norway. Poland. 

 S. Russia. Greenland. New Zealand (var.). United 

 States. W. Indies. Paraguay (var.). 



We think this Desmici is better regarded as a species of 

 Euastrum rather than of Cosmarium on account of the retuse- 

 emarginate apex of the semi-cells, with which is associated a 

 relatively large central protuberance. It is essentially an 

 upland species. 



Var. dissimile Nbrdst, (PL XLV, fig. 7.) 



Cosmarium snblobatum (Breb.) Arch, subsp. dissimile Nordst. Desm. Ital. 

 1876, p. 39, t. 12, f. 15. 



Cells less deeply constricted, the breadth of the 

 isthmus being about two-thirds that of the cell. Angles 

 of semicells dissimilar ; in vertical view with the 

 superior angles truncate and the inferior angles retuse. 

 Side view of semicell broadly truncate-pyramidate, with 

 a small basal tumour. 



Length 26-28*5 ^; breadth 17-20/x; breadth of 

 isthmus 12-13 JJL ; thickness 13-14 ^. 



SCOTLAND.- -Loch Luichart, Boss ! 



ICELAND.- -Dublin and Wicklow (Archer). 



Geogr. Distribution. Italy. 



Var. subdissimile var. nov. (PL XL, fig. 20.) 

 Cells with a broader isthmus ; semicells with larger 



