COSMAK1UM. 137 



Cells large, circular, about as long as broad, deeply 

 constricted, sinus very narrow and linear, dilated at 

 the extremity ; semicells semicircular with rounded 

 basal angles. Side view of semicell rounded-ovate or 

 subcircular. Vertical view narrowly elliptic, ratio of 

 axes 1:2-6. Cell-wall punctulate. Chloroplasts axile, 

 each with two pyrenoids. 



Zygospore unknown. 



Length 54-95 /A; breadth 54-90 ^; breadth of 

 isthmus 22-28 ^; thickness 25-38/1. 



ENGLAND. --Mickle Fell, X. Yorks ! 



"WALES. Snowdon, Carnarvonshire ! 



SCOTLAND. Loch Ruthven, Inverness ; near Loch 

 Mharc, in Athole, Perth (Ron $ Bissett). 



IRELAND.- -Creggan Lough, Gralway ! 



(leog-r. Distribution. Germany. Galicia in Austria. 

 Hungary (var.). Sweden. S. Russia, India. E. 

 Africa. United States. Brazil. 



C. circulars Reiiisch differs from C. Ralfsii Breb. in the 

 outward form of its cells and in its axile chloroplasts. The 

 semicells of C. circular e are semicircular in outline and never 

 exhibit the pyramidate character which is so conspicuous in 

 C. Ralfsii. 



C. circulare is distinguished from C. Lundellii Delp. by its 

 semicircular semicells and its elliptical vertical view. The 

 vertical view of C. Lundellii is drawn out at the poles and is 

 sometimes almost rhomboid-elliptic, whereas that of C. circu- 

 lar e is narrowly elliptic. There is also a thickening of the 

 cell-wall in the centre of the semicells of C. Lundellii which is 

 never present in C. circulare. 



Forma minor nob. (PI. LVI, fig. 12.) 



Cosmarium circulare Eacib. N"onn. Desm. Polon. 1885, p. 83, t. 11, f. 1. 



C. Raciborslcianum De Toiii, Syll. Alg. 1889, p. 975. 



Ursinella Raciborskiana Kuntze, Eevis. gen. plant. 1891, p. 925. 



Length 33-35 ju; breadth 35 p. ; breadth of isthmus 

 12-14 p. ; thickness 19 JLC. 



IRELAND. Creggan Lough, Galway ! 

 Geogr. Distribution. Poland. 



