14 BRITISH DESMIDIACE^:. 



(Roy). Essex! Warwick (Wills). Surrey! (Ralfs). 

 Sussex (Ralfs). Hants. ! (Ralfs). Devon! Cornwall! 



WALES.- -Fairly general ! 



SCOTLAND. General ! (Roy $ Bissett). Zygospores 

 from Powlair, Aberdeen (Roy fy Bissett). Outer 

 Hebrides ! Orkneys ! Shetland s ! 



IRELAND. Donegal ! Mayo ! Gal way ! Kerry ! 

 Dublin and Wicklow (Archer). Zygospore from Carrick 

 Mountain, Wicklow (Archer). Down! Londonderry! 



Geogr. Distribution.- -France. Germany. Austria 

 (var.) and Galicia. Hungary. Italy. Norway. 

 Sweden. Denmark. Bornliolm. Finland. Poland. 

 ]SL, Central, and S. Russia, Faeroes. Greenland. 

 Japan. United States. Brazil. 



This is a large and handsome Desmid which is generally 

 distributed throughout the British Islands. The figures given 

 by Ralfs are not very accurate except for the outline. That 

 author failed to depict the two small, central protuberances in 

 each semicell, and his vertical view is very erroneous. Between 

 and slightly below these central protuberances a large scro- 

 biculation is frequently present ; this form has been named 

 " forma scrobiculata Nordst." 



There are no protuberances on the front surface of the polar 

 lobe such as are indicated by Ralfs and other observers. This 

 is seen at once from the vertical view. The protuberances 

 figured by Ralfs and others on the polar lobes of many species 

 of this genus are frequently due to the refraction caused by 

 the vertical emarginatioii of each side of the polar lobe. 



Var. cephalophorum West, (PI. XXXV, fig. 1.) 



E. oblongum Wolle, Desni. U.S. 1884, t. 25, f. 6. 



E. oblongum (Grev.) Ealfs var. cephalophorum West, New Brit. Freshw. 

 Alg. ]S94, p. 4 ; Roy & Biss. Scott. Desni. 1894, p. 255. 



A variety with the lower interlobular incisions widely 

 open, and the upper interlobular incisions narrowly 

 linear ; upper lateral lobes much smaller than the 

 lower lateral lobes. 



Length loo/*,; breadth 90 /x; breadth of isthmus 



/*. 



SCOTLAND. Near the Spittal of Glen Shee, Perth ! 



