96 BRITISH DESMIDIACE^E. 



lobes divided into eight equal lobules by seven incisions 

 of which the median one is much the deepest, each 

 lobule furcate-dentate at its extremity ; margins of 

 interlobular incisions generally slightly undulate like 



the sinus. Side view of semicell linear-oblong, very 



' 



gradually attenuated to a tridentate apex. Vertical 

 view linear-fusiform, with acute poles and a slight flat- 

 tened protuberance in the middle on each side. Cell- 

 wall delicately punctate. 



Zygospore unknown. 



Length 162-191 p.; breadth 158-192 p; breadth of 

 polar lobe (at apex) 36-38 p.; breadth of isthmus 

 17-18 /i. 



ENGLAND. Bowness, Westmoreland ! Near Chapel 

 Wood, S.E. Surrey! Cornwall (Marquand). 



WALES. Capel Curig, Carnarvonshire (Gooke ^ 

 Wills) \ Llyn Grwernan near Dolgelly, Merioneth 



(Ralfs). 



SCOTLAND.- -Slewdrum, Aboyne and Birsemore Lochs, 

 Aberdeen (Roy f Bissett). Rhiconich, and in the 

 plankton of Lochs Shin, Grhriama, and nan Cuinne, 

 Sutherland ! Plankton of Loch Fadaghoda, Lewis ; 

 near Tarbert, Harris ; and in the plankton of Loch 

 nan Eun, N. Uist, Outer Hebrides ! Plankton of Loch 



Beosetter, Br essay, Shetlands ! 



/ 



IRELAND. Lough Derryclare, G-alway ! Adrigole, 

 Kerry ! 



Geogr. Distribution. France. Italy. Sweden. Den- 

 mark. United States. Jamaica. Brazil. 



This is one of the most beautiful species of the genus and 

 has been recorded principally under the name of "Micras- 

 terias radiosa." The first recognizable mention of this 

 Micrasterias is that by Ehrenberg in 1843 under the name of 

 Euastrum Sol. 



Neither Ecliinella radiosa Acharius (in Weber and Mohr, 

 'Beitr. zur Naturkunde/ II, 1810, p. 340, t. 4, f. 4-15), nor 

 Ecliinella radiosa, Lyngbye (' Tantamen Hydrophyt. Danicse/ 

 etc., Hafnias, 1819, p. 208, t. 69, f. E) refer to anything of the 

 nature of a Micrasterias as the genus is at present understood. 

 Micrasterias radiosa Ag. (in c Flora/ 1827, p. 643) is simply a 



