82 BRITISH DESMIDIACE.E. 



mus 9-1 3 '5 p. ; diam. zygosp., without spines, 32-35 pt ; 

 length of spines 5-6 p. 



ENGLAND.- -Lunds Fell, N. Yorks ! 



WALES. Capel Curig, Moel Siabod, Llyn Bochlwyd 

 and Llyn-y-cwm-frynon, Carnarvonshire ! 



SCOTLAND.- -Shetlands, Sutherland, Ross, Moray, 

 Aberdeen, Kincardine, Forfar, Perth, Fife, Argyle, Arran ; 

 zygospores from Cambus O'May, Aberdeen (Roy&Biss.}. 

 Orkneys ! 



IRELAND. Glendowan, near Glenties, and Loughs 

 Anure, Clogher and Magrath, Donegal ! Achill Isle, 

 Mayo ! Dublin and Wicklow (Arch.}. 



Geogr. Distribution.- -France. Germany. Switzerland. 

 Austria. Norway. Sweden. Denmark. Finland. Faeroes. 

 Greenland. Azores. United States. 



101. Staurastrum subscabrum Nordst. 

 (PL CXL, figs. 3, 4.) 



St. subscabrum Nordst. Alg. aq. dulc. et Char. Sandvic. 1878, p. 16, t. 2, 

 f. 1 ; De Toni, Syll. Alg. 1889, p. 1177 ; West & G. S. West, Some N. 

 Amer. Desm. 1896, p. 260, t. 18, f. 12 ; Comere, Desm. de France, 1901, 

 p. 172, t. 12, f. 21 ; West & G. S. West, Alg. X. Ireland, 1902, p. 51, 

 Brit. Freshw. Phytoplaiikton, 1909, p. 203. 



Cells small, about as long as broad, nearly circular 

 in outline, deeply constricted, sinus narrow, some- 

 times even linear ; semicells subpyramidate- truncate, 

 broad at the base, apex subtruncate, lateral margins 

 slightly convex, about 6-8 granules visible along each, 

 the upper ones emarginate ; cell- wall provided with 

 verrucse arranged in decussating horizontal and longi- 

 tudinal rows, the median ones emarginate ; horizontal 

 series 4 in number, vertical series about 6 or 8. Vertical 

 view triangular, sides straight, each with about 4 or 6 

 emarginate verrucee, and another similar series just 

 within the margin, angles obtuse, with a few granules, 

 centre of apex smooth. Chloroplast axile with a central 

 pyrenoid in each semicell. 



Zygospore unknown. 



