194 BRITISH DESMIDIACE^:. 



Lochs Shin, Ghriama and nan Cuinne, Sutherland !, Loch 

 Shiel, Inverness !, Loch Tay, Perth ! and Loch Doon, 

 Ayr ! ; of Loch Fadaghoda, Lewis, Loch Laxadale, 

 Harris, and Loch nan Eun, N. Uist, Outer Hebrides ! 



IRELAND. Near Lough Magrath, Donegal ! Bally- 

 nahinch and lakes east of Lough Bofin, Galway ! Plank- 

 ton of Galway and Kerry ! 



Geogr. Distribution. Germany. Norway. Sweden. 

 Finmark. Finland. United States. Alaska. Brazil (var.). 



This beautiful species is only found in the western parts of 

 the British Isles, and is most abundant in plankton. The length 

 of the processes tends to vary somewhat, but their arrangement 

 is constant. 



175. Staurastrum sexangulare (Bulnh.) Lund. 

 (PI. CLVII, figs. 2, 3.) 



Didyrnodadon sexangulare Bulnh. in Hedwigia, 1861, p. 51, t. 9 A, f. 1. 



Staurastrum sexangulare Lund. Desm. Suec. 1871, p. 71, t. 4, f. 9 ; Arch, 

 in Grevillea, 1881, p. 30 ; Cooke, Brit, Desm. 1887, p. 178, t. 62, f. 3, 

 t. 64, f. 4 ; De Toni, Syll. Alg. 1889, p. 1224 ; Borge ; Bidr. Sibir. Chlor. 

 1891, p. 10 ; Roy & Biss. Scott. Desm. 1893, p. 25 ; Comere, Desm. de 

 France, 1901, p. 159, t. 11, f. 6 ; West & G. S. West, Alg. Ceylon, 1902, 

 p. 181 ; Scott. Freshw. Plankton, 1903, p. 550 ; British Freshw. Phyto- 

 plankton, 1909, p. 202. 



St. furcato-stellatum Reinsch, Contrib. Alg. et Fung. 1875, p. 85, t. 16, f. 1. 



Didymodadon Stella Mask. N. Zeal. Desm. 1881, p. 308, t. 11, f. 9. 



Staurastrum Stella Mask. N. Zeal. Desm. Add. 1883, p. 254. 



Cells of medium or large size, usually a little longer 

 than broad, excluding the processes, deeply constricted, 

 sinus acute, open ; semicells elliptical or subfusiform, 

 apex slightly convex, lower margin slightly ventricose, 

 produced at the lateral angles, which are deeply cleft, 

 to form an upper and a lower process ; semicells with a 

 corresponding upper and lower Avhorl of processes 

 stretching horizontally across the semicell (about 4 or 

 5 pairs visible) ; processes of lower whorl nearly hori- 

 zontal or very slightly converging, those of upper whorl 

 diverging ; processes tipped with 3 or 4 spines and with 

 2 or 3 series of denticulations. Vertical view usually 

 5-7- (4-8-) radiate ; lateral margins deeply concave, with 

 a pair of flattened granules just within ; angles pro- 

 duced to form long tapering processes, with an upper 



