178 BRITISH DESMIDIACE^E. 



process projecting obliquely across each lateral margin 

 near the angle. Cell-wall smooth. 



Zygospore unknown. 



Length, without processes, 30-32 [JL ; including pro- 

 cesses, 52-61 [Ji ; breadth, including processes, 50-57 [j.; 

 breadth of isthmus 11 '5-17^. 



SCOTLAND. Brin, and in Skye, near Loch Cornisk, 

 Inverness ; Glen Coe, Argyle (Roy & Biss.}. Rhiconich, 

 Sutherland ! Plankton of Loch Fadaghoda, Lewis, Outer 

 Hebrides ! 



IRELAND.- -Kylemore, Co. Galway (Arch.). 



Geogr. Distribution. Norway. Sweden. Finland. 

 United States. 



164. Staurastrum Tohopekaligense Wolle. 

 (PL CLV, fig. 12.) 



Staurastrum Tohopekaligense Wolle, in Bull. Torr. Bot. Club. 1885, p. 128, 

 t. 51, f. 4, 5 ; Freshw. Alg. U. S. 1887, p. 45, t. 59, f . 4, 5 : De Toni, Syll. 

 Alg. 1889, p. 1162 ; West & G. S. West, Alg. Ceylon, 1902, p. 180 ; Alg. 

 Third Tanganyika Exp. 1907, p. 130, t. 3, f. 15. 



Cells large, about 1| times longer than broad, without 

 the processes, deeply constricted, sinus acute, narrow 

 at first, then opening widely ; semicells broadly oval or 

 subglobose, lateral angles produced to form long slender 

 processes usually with bifurcate spreading apices ; often 

 with 2 other similar processes between each pair of 

 angular processes ; with a further dorsal series of pro- 

 cesses, two of which project between each pair of 

 consecutive angles. Vertical view triangular or 

 quadrangular, sides straight or very slightly concave 

 or convex, angles produced into long slender processes, 

 with a pair of dorsal processes projecting from each 

 lateral margin, and frequently with a pair of processes 

 also on the same plane as the angular processes beneath 

 the dorsal series. 



Zygospore unknown. 



Length, without processes, 29-51 \i ; with processes, 

 48-91 \L ; breadth, without processes, 23-40 (x ; with 

 processes, 46-96 [i ; breadth of isthmus 13-19 k u. 



