164 BRITISH DESMIDIACE^E. 



154. Staurastrum cosmospinosum (Borg.) West. 



(PI. CLIV, figs. 5-7.) 



Staurastrum aculeatum subsp. cosmospinosum Borg. Bornholm. Desm.-fL 



1889, p. 147, t. 6, f. 8 : De Toni, Syll. Alg. 1889, p. 1218 ; West, Alg. 



W. Ireland, 1892, p. 184. 

 St. rostelhim Roy & Biss. Scott. Desm. 1893, p. 24, t. 3, f. 3 ; Borg. Alg. 



Faeroes, 1901, p. 233, t. 7, f. 15 ; Borge, Botan. Notiser, 1913, p. 50. 

 St. cosmospinosum West & G. S. West, Notes Alg. II, 1900, p. 295 ; Alg. 



N. Ireland, 1902, p. 48; Notes Alg. Ill, 1903, p. 11 ; Brit. Freshw. 



Phytoplankton, 1909, p. 202. 



Cells rather under medium size, slightly longer than 

 broad, deeply constricted, sinus acute and open ; semi- 

 cells elliptical, dorsal margin rather more strongly 

 convex than the ventral, lateral angles scarcely produced, 

 but provided with a large spine more conspicuous than 

 the others and often drooping towards the sinus ; with 

 several other smaller spines scattered in the vicinity of 

 the angles ; apex of semicell with a row of spines, some 

 of which tend to become emarginate ; faces with de- 

 cussating rows of smaller spines arranged in about 

 4 vertical and 3 horizontal lines. Vertical view quad- 

 rangular, sides very slightly concave, angles scarcely 

 produced, lateral margins spiny and with 1 or 2 rows of 

 spines just within the margin. 



Zygospore unknown. 



Length 31-43 fi ; breadth 29-38 JJL ; breadth of isth- 

 mus 13-14[ji. 



WALES. Capel Curig, Carnarvonshire ! 



SCOTLAND. Near Tain and Strathpeffer, Koss ; Glen 

 Sligachan in Skye, and Glen Nevis !, Inverness ; many 

 localities from Scotston to Girnoc, Aberdeen ; Rickarton, 

 Kincardine ; Glen Garry, Perth ; Glen Coe, Argyle (Roy 

 & Biss.}. 



IRELAND. Clifden to Roundstone, Galway ! Carran- 

 tuohill, Kerry ! Slieve Donard, Down ! 



Geogr. Distribution. Sweden. Bornholm. Faeroes. 

 Azores. 



