156 BRITISH DESMIDIACE^E. 



the processes, constricted at the middle, sinus short and 

 obtuse ; semicells broadly cuneate, or cup-shaped, apex 

 smooth and convex ; lateral margins nearly straight, 

 upper angles produced to form very long slender pro- 

 cesses, gently curved obliquely upwards, tipped with 

 3 small spines, and with many transverse series of den- 

 ticulations. Vertical view 9- or 10-radiate, apex smooth. 



Zygospore unknown. 



Length, without processes, 69-78 ^ ; with processes, 

 90-1 20 (Jt ; breadth, without processes, 43-48 y. ; with 

 processes, 130-140 (i ; greatest length of processes, 50 n ; 

 breadth of isthmus 24-26 [i. 



IRELAND. Bally nahinch and Derryclare Lough, Gal- 

 way ! 



This species is readily distinguished from St. Opkiitra Lund, 

 by its smooth apex, and slightly diverging processes. From 

 St. verticittatum Arch, it is distinguished by the different form of 

 the semicells. 



149. Staurastrum elongatum Barker. 

 (PL CLI, figs. 2-5.) 



Staurastrum elongatum Barker, in Quart. Journ. Micr. Sci. vol. 9, 1869, 

 p. 424; Wolle, Desm. U.S. 1884, p. 130. t, 40, f. 11, 12; Cooke, Brit. 

 Desm. 1887, p. 172, t. 59. f . 2 ; De Toni, Syll. Alg. 1889, p. 1212 ; Roy 

 & Biss. Scott. Desm. 1893, p. 19 ; West & G. S. West, Desm. U. S. 1898, 

 p. 317 ; G. S. West, Brit, Freshw. Alg. 1904, p. 172, f. (55 E ; West & 

 G. S. West, Brit, Freshw. Phytoplankton, 1909, p. 202. 



St. terebrans Nordst. Norges Desm. 1873, p. 34, t. 1, f. 16. 



Cells large, about 6 times longer than broad, excluding 

 the processes, constriction slight, sinus acute and open ; 

 semicells elongated cvathiform, considerablv swollen at 



/ / 



the base, where there are 3 or 4 close decussating rows 

 of granules ; apex convex, somewhat truncate in the 

 middle, with 2 emarginate verruca?, and two others just 

 beneath ; sides concave ; upper angles produced to 

 form short stout processes, parallel or very slightly 

 divergent, tipped with 3 minute spines, and with 2 or 

 3 series of acute denticulations. Vertical view triangular, 

 sides concave with 2 median emarginate verrucse, and 



