26 BRITISH DESMIDIACE^;. 



Index Desm. 1896, p. 93 ; West & GK S. West, Alg. S. England, 1897, 

 p. 483 ; Alga-fl. Yorks. 1900, p. 62 ; Alg. X. Ireland, 1902, p. 28. 



Helierella cuneata Kuntze, Eevis. gen. plant. 1891, p. 898. 



Euastrum cuneatum forma punctata Schmidle, Beitr. Algenfl. Rheineb. 11. 

 Schwarzwald, 1895, p. 80. 



Cells moderately large, more than twice as long as 

 broad, deeply constricted, sinus narrowly linear with 

 the extremity dilated; semicells narrowly pyramidate, 

 basal anoies slightly rounded and often a little thick- 



o o / 



ened, lateral margins almost straight (generally faintly 

 sinuate), apical angles slightly rounded, apex truncate 

 with a narrow and fairly-deep median incision ; semi- 

 cells without protuberances, or with a very slight 

 swelling within each basal angle. Side view of semi- 

 cell ovate-pyramidate, apex truncately rounded. Ver- 

 tical view broadly elliptic, lateral margins convex or 

 very slightly triundulate, Cell- wall finely scrobiculate. 



Zygospore unknown. 



Length 96-128 /x; breadth 47-59 /x ; breadth of 

 isthmus 13-22 ft; thickness 42 /x. 



ENGLAND.- -Cumberland ! Westmoreland! (Bissett). 

 W. and X. Yorks ! Lancashire ! Surrey ! Sussex 

 (Rolfs). Hants (Bennett). 



. General throuhout Carnarvonshire ! Ffes- 



tiniog !, and Dolgelly (Ralfs), Merioneth. 



SCOTLAND. Sutherland, Ross, Inverness, Aberdeen ! , 

 Kincardine, Forfar, Perth ! , Dumfriesshire (Roy $ 

 Bissett). Kirkcudbright ! Outer Hebrides ! 



IRELAND. Near Loughs Glentornan and Macgrath, 

 Donegal ! Jar Connaught and near Oughterard, Galway ! 

 Carrantuohill, Kerry ! Dublin and Wicklow, (Arclier). 

 Lough Fea, Londonderry ! 



Geofj-r. Distribution.- -France. Germany. Galicia in 

 Austria. Norway. Sweden. X. Eussia. Greenland. 

 Australia. Xew Zealand (var.). United States. 



This characteristic species is often abundant amongst sub- 

 merged Sphagnum in association with E. ampullaceum, Cos- 

 marium Oucurbita, Micrasterias tr-nncata, Eremosphserq viridis, 

 and other Alga?. We do not know of any near relatives to 

 E. cuneatum. The broadly-truncate apices, pyramidate semi- 

 cells, and absence of protuberances are all peculiar features. 



