22 BRITISH DESMIDIACE^E. 



53. Staurastrum aristiferum Ralfs. 

 (PI. CXXXII, figs. 10, 11.) 



Staurastrum aristiferum Ralfs, Brit. Desm. 1848, p. 123, t. 21, f. 2 ; Arch, 

 in Pritch. Infus. 1861, p. 737 ; Rabenh. Flor. Europ. Alg. 1868, p. 204 ; 

 Wood, Freshw. Alg. N. Amer. 1873, p. 149 ; Kirchn. Alg. Schles. 1878, 

 p. 169 ; Turn. Alg. Strensall Common, 1883, f. 6 ; Wolle, Desm. U. S. 

 1884, p. 122, t. 40, f. 15, 16 ; Cooke, Brit. Desm. 1887, p. 141, t. 49, f. 6 ; 

 De Toni, Syll. Alg. 1889, p. 1141 ; Roy & Biss. Scott. Desm. 1894, p. 17 ; 

 Cornere, Desm. de France, 1901, p. 163, t. 13, f. 15 ; West & G. S. West, 

 Alga-fl. Yorks, 1902, p. 96 ; Cushrnan, in Bull. Torr. Bot. Club, 1907, 

 p. 614 ; West & G. S. West, Brit. Freshw. Phytoplankton, 1909, p. 203. 



Cells small, a little longer than broad, not including 

 the spines, very deeply constricted, sinus acute, opening 

 widely, with a small incision at its apex ; semicells 

 triangular in outline, the central part somewhat tumid, 

 angles rather inflated and produced obliquely upwards, 

 ending in a long spine ; apex of semicell truncate or 

 slightly inflated in the middle ; lateral margins with 

 two slight undulations. Vertical view usually quad- 

 rangular, rarely triangular, lateral margins in the 4- 

 angled specimen strongly concave, in 3-angled specimens 

 convex in the middle, angles projecting and ending in 

 a long spine. 



Zygospore unknown. 



Length, without spines, 26-30 [JL ; breadth, without 

 spines, 24-27 \L ; breadth of isthmus 6-7 (ji ; length of 

 spines 14-19 pi. 



ENGLAND. Brother's Water, Westmoreland ! Mickle 

 Fell ! and Strensall Common (W. B. Turn.), N. Yorks. 



WALES. Capel Curig ! (Cooke & Wills] and Llyn-y- 

 cwm-ffynon, Carnarvonshire ! Dolgelly, Merioneth (Ralfs). 



SCOTLAND. Inverness, Aberdeen, Kincardine, Perth 

 and Dumbarton (Roy & Biss.). Rhiconich, Suther- 

 land ! 



IRELAND. Achill Island, Mayo ! Derryclare Lough 

 and Kylemore, Co. Gal way ! 



Geogr. Distribution.- -France. Germany. Austria. 

 Norway. Sweden. India. Australia. United States. 

 Brazil. 



