STAURASTRUM. 177 



margin more convex ; each angle of the cell with 4 pro- 

 cesses, an upper pair and a lower pair, processes bifid 

 at the apex, the two teeth lying in the same vertical 

 plane. Vertical view triangular, sides slightly concave, 

 angles broadly truncate and bifid, a lower pair of short 

 processes visible under an upper pair at each angle. 

 Cell- wall smooth or minutely punctate. 



Zygospore unknown. 



Length, without processes, 17-25 y, ; including pro- 

 cesses, 26-30 fji ; breadth, including processes, 20-26 y. ; 

 breadth of isthmus 7*7-10[i. 



SCOTLAND. Glen Shee, Perth ! 



Geogr. Distribution.- -Poland (form). Ceylon. United 

 States. Colombia (form). Brazil. 



This species should be compared with St. quadrangulare Breb., 

 which differs in the possession of four solid spines at each angle. 



163. Staurastrum Clevei (Wittr.) Eoy & Biss. 



(PL CLVI, fig. 6.) I 



Staurastrum Icece Cleve, Sverig. Desm. 1863, p. 490. 



St. Iceve var. Clevei Wittr. Skand. Desm. 1869, p. 18, t. 1, f. 9 ; Arch, in 

 Quart. Journ. Micr. Sci. vol. ii, 1871, p. 92 ; Cooke, Brit. Desin. 1887, 

 p. 180, t. 63, f. 3 ; Eichler, Mat. Flor. Miedz. 1894, p. 62. 



St. KitcMlii Wolle, Desm. U. S. 1884, p. 150, t. 40, f. 35, 36 ; De Toni, Syll. 

 Alg. 1889, p. 1155 ; West & G. S. West, Desm. U. S. 1898, p. 319, t. 18, 



f. 10, 11. 



St. Clevei Roy & Biss. Scott. Desm. 1893, p. 18 ; Wittr. & Nordst. Alg. 

 Exs. fasc. 35, 1903, p. 12 ; West & G. S. West, Further Contrib. Plankton 

 Scott. Lochs, 1905, p. 503 ; Brit. Freshw. Phytoplankton, 1909, p. 202. 



Cells rather under medium size, slightly longer than 

 broad, excluding the processes, deeply constricted, sinus 

 acute and open ; semicells subelliptic, lower margin 

 strongly ventricose, dorsal margin slightly convex, 

 lateral angles gradually produced to form fairly long 

 processes, deeply bifid with spreading apices in the same 

 vertical plane ; each face of the semicell with another 

 process, inserted obliquely near to each angular process. 

 Vertical view triangular, angles produced to form pro- 

 cesses, sides slightly convex, apex with an accessory 



VOL. v. 12 



