EUASTKUM. 65 



they are often sharp and conical. Side view of semi- 

 cell widely inflated in the lower part owing to the 

 verrncose central protuberances showing at each side, 

 then narrowed to form a " neck " ; apical portion dilated, 

 angles rounded, apex retuse. Vertical view elliptic, 

 poles mamillate and granulate, with three large sub- 

 verrucose protuberances on each side, upper and lower 

 lateral lobules entire ; polar lobe oblong-rectangular, 

 with retuse sides and rounded angles. 



Zygospore unknown. 



Length 93-114 //,; breadth 75-92 /LL; breadth of 

 isthmus 19-22 p. ; thickness 53-55 JJL. 



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

 TT. and N. Yorks ! Lancashire ! Leicestershire (Roy). 

 Warwick (Wills). Middlesex (Has sail). Surrey! 

 (Ralfs). Sussex (Rolfs). Kent! (Rolfs). Hants! 

 (Rolfs). Cornwall! (Ralfs). 



WALES. Capel Curig ! (Gooke $ Wills), Llyn 

 Ogwen !, Grlyder Fawr (Roy), Carnarvonshire. 



SCOTLAND.- -Generally distributed ! (Roy Bissett). 

 Frequent in the plankton ! Shetlands ! 



IRELAND.- -Donegal ! Mayo ! G-alway ! Kerry ! 

 Dublin and AYicklow (Archer). Armagh ! London- 

 derry ! 



G-eogr. Distribution. France. Germany. Galicia in 

 Austria. Hungary. Italv. Xorwav. Sweden. Den- 



O t/ . tJ 



mark. Bornholm. Finland. Poland. TT., Central, 

 and S. Russia. Faeroes. Greenland. Siberia. Japan. 

 India. Australia. Central Africa. United States. 

 Uruguay. Argentina. 



E. verrucosum is not so abundant as some of the other large 

 species of Euastrnm. It is not often found in bogs, having' a 

 decided preference for the margins of large, reedy ponds and 

 lakes. It cannot easily be confused with any other species 

 of the genus. 



Var. reductum Norclst. (PI. XL, figs. 2, 3.) 



E. verrucosum var. reductum Nordst. Alg. et Char. I, 1880, p. 9, t. 1, f . 14 ; 

 De Toni, Syll. Alg. 1889, p. 1067 : West & G. S. West, Alg. N. Ireland, 

 1902, p. 27 ; Scott, Freshw. Plankton, I, 1903, p. 525. 



VOL. II. 5 



