190 BRITISH DESMIDIACEJE. 



Cells with a more open sinus ; semicells with rounder 

 basal angles, convex lateral margins, and relatively 

 broad apices. 



Length 28 (JL; breadth 17-1 8 ft; breadth of isthmus 

 5-2-67 p.. 



SCOTLAND. Break Xeck Fall in (lien Callater, 

 Aberdeen (Roy fy Bissett). 



Geocjr. Distribution. Island of Banka. 



We have not seen this variety and cannot definitely state 

 whether it is correctly placed under Cosmarium granatum or 

 not. We give a copy of Grimow's figures, which are not 

 very good. 



41. Cosmarium Pokornyanum (Grim.) West & G. S. 



West. 



(PL LXIII, figs. 11-15.) 



Euastrum Pokornyanum Grun. in Rabenh. Flor. Europ. Alg. Ill, 1S6S, 



p. 185 ; De Toni, Syll. Alg. 1889, p. 1073 ; Hansg. Prodr. Algenfl. Bohin. 



1892, II, p. 175. 

 E. binale (Turp.) Ehrenb. var. angnstatum Wittr. Gotl. Ol. sotv. Alg. 



1872, p. 50, t. 4, f. 8 ; Cooke, Brit. Desm. 1886, p. 75, t. 35, f . 9. 

 E. polare Nordst. Desm. Spetsb. 1872, p. 37, t. 7, f. 24. 

 Cosmarium angustatum (Wittr.) Nordst. Desm. Arctoae. 1875, p. 20 ; 



Wille, Ferskv. Alg. Nov. Semlj. 1879, p. 39, t. 12, f. 36; Boldt, Desmid. 



Gronlaiid, 1888, p. 12; De Toni, Syll. Alg. 1889, p. 1044; Heimerl, 



Desm. alpin. 1891, p. 599; West, Alg. W. Ireland, 1892, p. 143 ; Lutkem. 



Desm. Attersees, 1893, p. 550; Roy & Biss. Scott. Desm. 1894, p. 41; 



Nordst. Index Desm. 1896, p. 45; G. S. West, Alga-fl. Cambr. 1899, 



p. 217. 

 C. Pokornyanum (Grun.) West & G. S. West, Notes Alg. II, 1900, p. 292 ; 



Alga-fl. Yorks. 1900, p. 79 ; Alg. N. Ireland, 1902, p. 32. 



Cells small, about twice as long as broad, or nearly 

 so, deeply constricted, sinus narrow, generally linear 

 with a slightly-dilated apex ; semicells subtrilobed or 

 truncate-pyramidate from a base with parallel sides, 

 basal angles rectangular, lower part of sides parallel, 

 generally slightly retuse (rarely straight), upper part 

 of sides longer, converging and widely concave, apex 

 truncate and slightly retuse, upper angles rounded. 

 (In those forms which are subtrilobed the apical lobe 

 is subquadrate.) Side view of semicell ovate-truncate. 

 Vertical view rhomboid-elliptic, ratio of axes about 



