MICKASTERIAS. 117 



Hampsfell, Lancashire ! Cheshire (Rolfs). Norfolk 

 (Coolie). Sussex (Ralfs). Hants (Bennett). 



WALES.- -Dolgelly, Merioneth (Ralfs). 



SCOTLAND.- -Scotston Moor, Brimmond, near Old 

 Meldrum, Slewdrum, Birsemore Loch, Tomachar, 

 and Homehead in Croniar, Aberdeen ; near Cammie 

 in Strachan, Kincardine; Clova Tableland, Forfar; 

 Durdie, Perth (Roy $ Bissett). 



IRELAND. Creggan. Lough, Ballynahinch, and loughs 

 near Recess, Galway ! Dublin and Wicklow (Archer). 



Geogr. Distribution. France. Germany. Austria. 

 Galicia. Hungary. Italy. Sweden. Denmark. 

 Poland. N. and S. Russia. Japan. N. India. 

 Ceylon. Burma. Celebes. Madagascar (var.). Cen- 

 tral Africa. United States. Brazil. 



The variation of this species is principally confined to the 

 subdivisions of the lateral lobes. The two lobules of each 

 lateral lobe are normally somewhat truncate and hidentate, 

 but occasionally some or all of the lobules are tridentate or 

 even further divided by a fairly deep notch into two biden- 

 ticulate parts. One of these forms is figured on PI. LIII, 

 fig. 3, and Turner described another under the name of " var. 

 supeifiua." 



M. Crux-melitensis is a rare species, easily distinguished 

 from J/. radiata by its smaller size, and the much shorter and 

 stouter lobules, which are never deeply furcate. 



Forma punctulata West. 



M. C rux-rnelitensis forma punctulata West, Alg. Eng. Lake Distr. 1892, 

 p. 722. 



Cell-wall irregularly punctulate (or subgranulose), 

 causing the outline of the cell to appear minutely 

 papillate. 



Length 122 /^; breadth 1 1 5 p. ; breadth of isthmus, 21 p.. 



ENGLAND. Xear Bowness, Westmoreland ! 



17. Micrasterias Americana (Ehrenb.) Ralfs. 

 (PL LIII, figs. 4, 5; PL LIV, figs. 1-3.) 



Euastrum Americanum Ehrenb. Verbreitiing ti. Einfluss des microscop. 

 Lebens in Siid- 11. Nord-amerika, Physik. Abh. Preuss. Akad. d. Wiss. 

 zu Berlin, 1843, p. 413, t. 4, f. I 15. 



