STAURASTRUM. 73 



SECTION G. 



Cells with verruca? which are emarginate, or very much reduced 

 and 2- or 3-spmate. 



; Cells more than 1| times longer than broad. 



t Lateral margins with an incision or rounded concavitv 

 semicells angular. 



94. St. at:n, -ill as. 

 TT Lateral margins entire ; semicells subelliptic. 



95. St. aspenui'. 

 Cells about as long as broad or only slightly longer. 



t Verruca restricted to the angles and apex ; faces of 

 semicell smooth. 



96. St. maamense. 

 ft Verrucas more or less evenly distributed. 



J Verrucae surmounting distinct though short pro- 

 cesses pushed out from the cell- wall. 



97. St. spongiosum. 

 Jf Verrucse borne directly on the cell-wall. 



98. St. echinodermum. 



99. St. Amelia. 



100. St. scabrum. 



101. St. subscabrum. 



94. Staursatrum acarides Xordst. 

 (PL CXL, figs. 6, 7.) 



S7. <i.<:arides Xordst. Desm. Spetsb. 1872, p. 40, t. 7, f. 26; Joshua. Note- 

 on Brit. Desm. II, 1883, p. 292 ; Cooke, Brit. Desm. 1887, p. h>3. t. 60, 

 f. 5; De Toni, Syll. Alg. 1889, p. 1169; West, Alg. X. Yorks. 18N1. 

 p. 293 ; Roy & Biss. Scott. Desm. 1893, p. 16 ; Borge, Siisswasseralgen 

 Franz Josefs-Land, 1899, p. 764. 



Cells rather under medium size, about l : i times longer 

 than broad, oblong elliptic in outline ; constriction 

 moderately deep, sinus linear, dilated at its apex, semi- 

 cells pyramidate-truncate, somewhat angular, apex 

 broad and truncate, or often slightly concave, basal 

 angles almost rectangular, upper angles obtusely 

 rounded, lateral margins verrucose, with a small rounded 

 concavity just above the middle part ; semicells in front 

 view with several short longitudinal series of verruca*, 

 rather more crowded towards the angles. Vertical view 

 triangular, sometimes hexangular, lateral margins verru- 

 cose and slightly convex, angles bluntly rounded, with 



