38 BRITISH DESMIDIACE^E. 



Austria. Turkey-in-Europe. Norway. Sweden. Born- 

 holm. Finland. Poland. N. Eussia. Japan. Abyssinia 

 (var.). Central Africa (var.). West Indies (var.). Brazil. 

 Argentine (var.). 



66. Staurastrum quadrispinatum Turn. 

 (PL CXXXV, figs. 5-7.) 



St. quadrispinatum Turn. Notes Freshw. Alg. 1886, p. 35, t. 1, f. 4 ; Cooke r 

 Brit. Desm. 1887, p. 164, t. 55, f . 5 ; De Toni, Syll. Alg. 1889, p. 1199; 

 Johnson, Rare Desm. U. S. I, 1894, p. 289 ; West & G. S. West, Some 

 N. Amer.' Desm. 1896, p. 258, t. 18, f. 17 ; Borge, Nordamerik. Siiss- 

 wasseralg. 1909, p. 11. 



Cells small, li to Ij times longer than broad, not 

 including the spines, deeply constricted, sinus open and 

 acute ; semicells elliptic-oblong, broader at the base than 

 at the apex, often somewhat angular ; apex nearly flat, 

 ventral margin strongly convex, lateral margins trun- 

 cate, angles of the semicell provided with 4 stout and 

 strongly divergent spines, one pair at the upper and lower 

 extremities of the angle respectively. Vertical view 

 triangular, sides straight, angles broadly truncate, spines 

 so divergent as to be almost perpendicular to the lateral 

 margins, and nearly in a line with the truncate angles. 

 Cell- wall finely punctate. 



Zygospore unknown. 



Length, without spines, 33-39 \L ; breadth, without 

 spines, 26-30*5 [i ; breadth of isthmus 8-10'5 \L ; length 

 of spines lOfji. 



WALES.- -Trelleck Common, Monmouth (Turn.}. 



Geogr. Distribution.- -United States. 



This species is distinguished from St. quadrangulare Breb. by 

 its relatively greater length, and its stouter spines, wMchJare 

 also much more divergent. 



67. Staurastrum denticulatum (Nag.) Arch. 

 (PI. CXXXIII, figs. 13-15.) 



Phycastrum (Pachy actinium) denticulatum Nag. Gatt. einz. Alg. 1849, p 128 

 t. 8, C. f. 3. 



