STAURASTRUM. 155 



147. Staurastrum verticillatum Arch. 

 (PL CLI, figs. 7, 8.) 



Staurastrum verticillatum Arch, in Quart. Journ. Micr. 8ci. vol. 9, I860, 

 p. 196 : Cooke, Brit. Desm. 1887. p. 177, t. 61, f. 3 ; De Toni, 8yll. Alg. 

 1889, p. 1223 : West & G. S. West. Scott. Freslnv. Plankton, I, 1903, 

 p. 549, t. 14. f. 7. 



Cells large, nearly 3 times longer than broad, excluding 

 the processes, constriction slight, sinus acute ; semi- 

 cells almost cylindrical, slightly broader at the apex, 

 which is convex and almost smooth ; upper angles 

 produced to form long, strongly divergent processes 

 tipped with 2 or 3 minute teeth, and with many series 

 of denticiilations, the upper margin of the process con- 

 siderably rougher than the lower ; semicells with a ring 

 of papillae at the base, about 7 of which are visible in the 

 front view. Vertical view 8-10-radiate. processes very 

 long and tapering gradually, with denticiilations stronger 

 towards the base of the process, apex of semicell with a 

 pair of large verrucse near the base of each process. 



Zygospore unknown. 



Length, without processes, 76-79 u : with processes, 

 136-1 43 [JL ; breadth, without processes, about 26-28 k u. ; 

 with processes, 124-1 30 y. ; breadth of isthmus 20 pt. 

 [Note.- -The breadth without processes given by W. & 

 G. S. W., 'Scott. Fresliw. Plankt,' I, 1903. p/549, as 

 36-38 [JL is erroneous.] 



SCOTLAND.- -Rhiconich. Sutherland ! Plankton of 

 Loch Mor Bharabhais, Lewis, Outer Hebrides ! 



IRELAND.- -Near Maam, Galway (Arch.). 



Geogr. Distribution.- -France. Norway. 



The front view of this species is so characteristic that it can 

 readily be distinguished from both St. Ophiura Lund, and St. 

 Archerii West. Its processes are more slender and more diver- 

 gent than those of the latter species. 



148. Staurastrum Archerii West. 

 (PL CLIIL figs. 6, 7.) 



Staurastrum Archerii West, Alg. W. Ireland, 1892, p. 183, t. 23, f. 15. 



Cells large, about twice as long as broad, excluding 



