122 BRITISH DESMIDIACE.E. 



subrectangular, lower angles not rounded, practically 

 rectangular, apex very slightly convex, upper angles 

 produced to form long diverging processes, with 2 or 3 

 undulations and emarginate apices ; vertical view tri- 

 angular, sides nearly straight, angles produced into long 

 nodulose processes ; cell- wall smooth. 



Zygospore unknown. 



Length, without processes, 8-10 JJL ; including pro- 

 cesses, 1 3-20 (ji ; breadth, without processes, 6-9 \i ; 

 including processes, 13-21 fi ; breadth of isthmus 3*5- 



4(JL. 



ENGLAND.- -Puttenham Common, Surrey ! 



WALES. Capel Curig, Carnarvonshire ! 



SCOTLAND. --Near Girnoc, Aberdeen (Roy & Biss.). 

 Spital of Glen Shee, Perth ! Rhiconich, Sutherland ! 



Geogr. Distribution. Sweden (var.). Poland. Ceylon. 

 United States. 



126. Staurastrum pseudotetracerum (Nordst.) 



W. & G. S. West. 



(PL CXLIX, fig. 11.) 



Staurastrum contortum var. pseudotetracerum Nordst. in Botan. Notiser, 

 1887, p. 157 ; Freshw. Alg. New Zeal. 1888, p. 37, t. 4, f. 9 ; De Toni, 

 Syll. Alg. 1889, p. 1231 ; West, Alg. W. Ireland, 1892, p. 183. 



St. pseudotetracerum West & G. S. West, Alg. Madag. 1895, p. 79, t. 8, f. 39 ; 

 Desm. U. S. 1898, p. 314 ; Bohlin, Flor. Alg. d'eau douce d'Acores. 1901, 

 p. 58, t. 1, f. 16 ; West & G. S. West, Alga-fl. Yorks. 1902, p. 104 ; Alg. 

 Ceylon, 1902, p. 185. 



Cells very small, about as long as broad, including 

 the processes, deeply constricted, sinus widely open, 

 broadly triangular in outline; semicells cuneate, apex 

 nearly straight, or slightly convex or concave, upper 

 angles produced to form short, strongly diverging pro- 

 cesses tipped with 3 very minute spines ; processes 

 rough with subacute granules arranged in concentric 

 series. Vertical view triangular or quadrangular, sides 

 concave, angles produced to form granulose processes. 



Zygospore unknown. 



Length, without processes, 12-19(i ; with processes, 



