52 BRITISH DESMIDIACE^E. 



SCOTLAND. --Powlair, Slewdrum, Heughhead, Birk- 

 hill, Tomachar, Dinnet, Glen Clunie, Aberdeen ; near 

 Crathes, and near Durris Bridge, Kincardine ; Glen 

 Isla, Forfar (Roy & Biss.). 



Geogr. Distribution. Galicia in Austria. Faeroes. 



This species is nearest to St. asperum Breb. in the form of its 

 semicells, but the arrangement of the spines, which are almost 

 entirely confined to the angles, distinguishes it. 



78. Staurastrum setigerum Cleve. 

 (PL CXXXVI, figs. 13, 14.) 



St. setigeniiti Cleve, Sverig. Desm. 1864, p. 490, t. 4, f. 4 ; Rabenh. Flor. 



Europ. Alg. 1868, p. 216; Nordst. Norges Desm. 1873. p. 31 ; Welle, 



Desm. U. S. 1884, p. 141, t. 45, f. 26, 27 ; De Toni, Syll. Alg. 1889, p. 1168; 



Roy & Biss. Scott, Desm. 1894, p. 25, t. 3, f. 9 ; Eichler, Mat. Flor. 



Miedz. 1894, p. 62 ; Comere, Desm. de France, 1901, p. 167, t. 12, f. 2 ; 



Borge, Alg. erst, Regnell. Exped. II, Desm. 1903, p. 108 ; West & G. S. 



West, Brit. Freshw. Phytoplankton, 1909, p. 202 ; Borge, Sao Paulo 



Siisswasseralgen, 1918. p. 53. 

 St. Royanum Arch, in Quart. Journ. Micr. Sci. 1877, vol. 17, p. 103 ; Cooke, 



Brit. Desm. 1887, p. 152. 



Cells of medium size, a little longer than broad, 

 deeply constricted, sinus acute and open ; semicells 

 elliptical, ventral margin more convex than tbe dorsal, 

 angles obtusely rounded arid provided with 2-5 (usually 

 3) long stout spines arranged in a vertical row, or some- 

 times (according to Archer) in a circle like the shafts of 

 a shuttlecock. Surface of cell provided with a number 

 of long but more delicate spines than those at the angles, 

 arranged in distant obscure circles round the angles. 

 Vertical view triangular, sides nearly straight, angles 

 rather acutely rounded. Chloroplast axile, with a 

 central pyrenoid in each semicell. 



Zygospore unknown. 



Length, without spines, 50-56 \L ; breadth, without 

 spines, 42-45 [JL ; breadth of isthmus 14*5-17[Ji ; length 

 of angular spines 15-20[ji; length of more delicate 

 spines about 10-1 2 pi. 



WALES. Capel Curig, Carnarvonshire ! 



