166 BRITISH DESMIDIACE.E. 



ENGLAND. Thursley Common, Surrey ! 

 SCOTLAND.- -Upper Powlair in Birse, Aberdeen ; pool 

 by the Spital Burn, Strachan, Kincardine (Roy & 



Biss.). 



Geogr. Distribution. Austria. Scandinavia. 



156. Staurastrum Sebaldi Reinsch. 

 (PL CXLVIII, figs. 5, 6.) 



Staurastrum Sebaldi Reinsch, Spec. Gen. Alg. 1867, p. 133, t. 24 D, f. 1-3; 

 Nordst. Norges Desm. 1873, p. 33 ; Wolle, Desm. U. S. 1884, p. 138, t. 46, 

 f. 1-6; Cooke, Brit. Desm. 1887, p. 176; Borg. Bornh. Desm. 1889, 

 p. 148 ; De Toni, Syll. Alg. 1889, p. 1220 ; West, Desm. Massach. 1889, 

 p. 20, t, 3, f. 17 ; Alg. W. Ireland, 1892, p. 184 ; Eichler, Mat. Flor. 

 Miedz. 1894, p. 62 ; West & G. S. West, Some N. Amer. Desm. 1896, 

 p. 267, t. 18, f. 2, 3 ; Borg. Alg. Faeroes, 1901, p. 234. 



Didymidium (Staurastrum} Sancti Sebaldi Reinsch, Algenfl. Frank. 1867, 

 p. 175, t, 11, f. 1. 



Cells large, body of cell about 1| times longer than 

 broad, not including the processes, moderately con- 

 stricted ; sinus acute, opening widely ; semicells cup- 

 shaped, dorsal margin convex, angles produced to form 

 short, stout, tapering processes, which are usually slightly 

 converging and are tipped with 3 or 4 spines ; processes 

 with several concentric series of strong denticulations ; 

 apex of semicell with a row of large, simple, or 2-4-dentate 

 spines, and usually with a further row of simple spines 

 just beneath the apex, the lower series, however, variable 

 both in size and in character, sometimes even wanting. 

 Vertical view triangular, sides nearly straight, sometimes 

 a little convex, angles slightly produced into short den- 

 ticulate processes, with a series of simple or complex 

 spines within each lateral margin, which may itself be 

 spinous or not, according as the lower series of spines 

 is present or absent. 



Zygospore unknown. 



Length 73-85 ^ ; breadth, including processes, 69- 

 100 [Ji ; breadth of isthmus, about 24 [i. 



ENGLAND.- -Bowness. Westmoreland ! Strensall !, Gor- 

 mire (W. B. Turn.}, and Pilmoor !, N. Yorks. Malham 

 Tarn, W. Yorks ! 



