COSMARIUM. 83 



Cells rather small, a little longer than broad, deeply 

 constricted, sinus open and obtuse, with subparallel 

 sides ; semicells transversely subelliptic or subhexa- 

 gonal-elliptic, lateral angles obtuse, lower lateral 

 margins rather longer than upper lateral margins, 

 slightly convex, apex widely truncate-convex. Side 

 view of semicell subcirciilar. Vertical view sub- 

 rhomboid-elliptic, ratio of axes about 1 : 1*5. Cell- 

 wall very delicately punctate (often appearing smooth). 

 Chloroplasts axile, one in each semicell, with a central 

 pyrenoid. 



Zygospore globose and smooth. 



Length 20-41 p ; breadth 18-36 p. ; breadth of isth- 

 mus 8-10*5 ft; thickness 11-17 JJL ; diam. zygosp. (of 

 small form) 30 //,. 



EXGLAXD.- -Bowness, Westmoreland ! Epping Forest, 

 Essex ! Thursley Common, Surrey (with zygospores) ! 

 Xew Forest, Hants ! 



SCOTLAND.- -Loch Rutliveii and Clachan, Inverness 

 (Roy $ Bissett). 



Geor/r. Distribution.- -Germany. Gralicia in Austria. 

 Xorway. Sweden. Poland. Russian Lapland. Green- 

 land (var.). India. Xew Zealand (var.). Australia 

 (var.). Madagascar (var.). Central and East Africa. 

 United States. 



C. pseudoprotuberans exhibits considerable variation in size. 



It is distinguished from C. sexangulare by its less deep and 

 more open sinus, and by the more rounded character of its 

 apices. 



Xordstedt has described a trigonal variety (/3 trigonum} 

 from Greenland (ride Xordst. 'Desm. Gronland/ 1885, p. 7, 

 t. 7, f . 2) ; length 29 p ; breadth 26-28 p. 



Var. alpinum Racib. (PI. XCI, fig. 10.) 



C. pseudoprotuberans Kirclin. c. alpinum Racib. Xonn. Desin. Polon. 1885, 

 p. 83, t. 10, f. 11 ; Eoy & Biss. Scott, Desin. 1894, p. 172. 



Cells much smaller; semicells with the superior 

 lateral margins forming part of the apex, which is 

 relatively very wide ; sinus somewhat narrower. 



