STAURASTRUM. 113 



somewhat cup-shaped, upper angles produced to form 

 long, nearly horizontal or slightly diverging processes, 

 each provided with 4 series of denticulations, and with 

 3 spines at the extremity ; apex of semicell very slightly 

 produced, nearly straight and with acute emarginate 

 granules ; base of semicell with a circle of 11-13 den- 

 ticulations, of which 6 or 7 may be seen in the front view. 



J / 



Vertical view triangular, sides nearly straight, with 

 3 emarginate verrucse along each, and with 3 others just 

 within each lateral margin. 



Zygospore unknown. 



Length 27-29 JJL ; breadth, with processes, 43-46 [JL ; 

 breadth of isthmus 7 '5-8 (JL. 



SCOTLAND.- -Plankton of Loch Asta, Shetlands ! 



This species has only been recorded from one locality, 

 where it occurred in considerable abundance. It is not very 

 closely allied to any other British species, and should be com- 

 pared with. St. Burmense Turn, and St. galeatum Turn, (vide W. 

 & G. S. West, 'Freshw. Alg. Ceylon,' 1902, p. 190, t. 22, f. 19). 



119. Staurastrum Pseudosebaldi Wille. 

 (PL CLXVI, fig. 4.) 



Staurastrum Pseudosebaldi Wille, Norges Ferskv. Alg. 1880, p. 45, t. 2, f. 30 ; 

 \Volle, Desm. U. S. 1884, p. 139, t, 46, f. 8, 9 ; De Toni, Syll. Alg. 1889, 

 p 1178 ; Borge, Siissw. Chlor. Archang. 1894, p. 38 ; W. & G. S. West, 

 A\v S. England, 1897, p. 496 ; Borg. Alg. Faeroes, 1901, p. 235, t. 7, 

 f. 17 ; West & G. S. West, Alga-fl. Yorks. 1902, p. 106 ; Cushman in 

 Rhodora, 1903, p. 224. 



Cells of medium size, about 1 times broader than long, 

 including the processes ; body of cell slightly constricted, 

 sinus an acute notch; semicells cuneate, slightly 

 campanulate at the base, widening towards the apex, 

 lateral margins concave ; upper angles produced into 

 stout horizontal processes, each tipped with three spine 

 and rough with several concentric series of granules 

 apex of semicell with a row of regular bifid spines 

 base of semicell with a series of distant granules ot which 

 3 are visible. Vertical view triangular, lateral margins 



VOL. V. 



