150 BRITISH DESMIDTACE^E. 



conical granules having no regular disposition, 14 or 

 15 showing at the margin. Vertical view circular. 

 Chloroplasts axile, one in each semicell, with a central 

 pyrenoid. 



Zygospore subglobose, furnished with conical warts, 

 about 20 visible at the margin. 



Length 35-38 /u ; breadth 18-20 1.1 ; breadth of 

 isthmus 6'5-8ju; diam. zygosp. without warts 30 /u, 

 with warts 35 /*. 



ENGLAND.- -Westmoreland (Ealfs). Mickle Fell and 

 Strensall Common, N. Yorks ! Cullingworth, W. 

 Yorks ! Bisley Common, Surrey! Sussex (Ealfs). 

 New Forest, Hants ! Cornwall (Ralfs). 



WALES. Capel Curig ! (Coolce fy Wills), Llyn 

 Padarn and near Bettws-y-Coed, Carnarvonshire ! 



SCOTLAND.- -Sutherland ! Inverness, Aberdeen, Kin- 

 cardine, Forfar, Perth, Argyll (Roy fy Blssett). 



IRELAND. --Near Grlenties, Donegal! Ballynahinch, 

 Galway ! Adrigole, Castletown, and Carrantuohill, 

 Kerry! Dublin and \Yicklow (Archer). Slieve Donard, 

 Down ! 



Geogr. Distribution. France. Germany. Galicia. 

 Italy. Norway. Sweden. Finland. Greenland. 

 United States. 



C. orbicidatum is a characteristic species of somewhat rare 

 occurrence. The zygospore is somewhat similar to that of 

 C. isthmium, but the warts are not trimcate-emarginate. 



Forma major. (PI. LXXVII, fig. 18.) 



Length 55^; breadth 28ft; breadth of isthmus 

 12-5 ,*. 



WALES.- -Capel Curig, Carnarvonshire ! 



150. Cosmarium praegrande Lund. 

 (PI. LXXVII, fig. 19.) 



Cosmarium praegrande Lund. Desni. Suec. 1871, p. 54, t. 3, f. 21 ; Boldt, 

 Desmid. Gronland, 1888, p. 28 ; Borg. Bornh. Desm.-fl. 1889, p. 146, 

 t. 6, f. 7 ; Borge, Siissw. Chlor. Archang. 1894, p. 19 ; Eoj- & Biss. Scott. 

 Desm. 1894, p. 171 ; Nordst. Index Desm. 1896, p. 205. 



Cosmaridium prsegrande Hansg. Prodr. Algenfl. Bohni. 1888, p. 246. 



Plenrotxniopsis prsegrandis (Lund.) De Toni, Syll. Alg. 1889, p. 913. 



