COSMAEIUM. 41 



characteristic. C. cymatonotophorum is a minute species and 

 is easily overlooked. It generally occurs very sparingly i n a 

 gelatinous matrix containing many other Algae and much 

 extraneous material. 



71. Cosmarium rectangulum Reinscli. 

 (PL LXIX, fig. 1.) 



Cosiiiarinm rectangulum Reinscli,, Contrib. Alg. et Fung. 1875, p. 89 ; 1. 10, 

 f. 9 ; De Toni, Syll. Alg. 1889, p. 104U; Eoy & Biss. Scott. Desm. 1894,' 

 p. 173; Xordst. Index Desm. 1896, p. 222. " 



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



Cells rather small, about as long as broad, deeply 

 constricted, sinus rather narrow but not quite closed, 

 slightly widened at the apex; semicells transversely 

 rectangular, sides o-undulate (including upper and 

 lower angles), apex widely truncate and 4-undulate. 

 Vertical view elliptic (r). Cell-wall smooth. 



Zygospore unknown. 



Length 28' o ju, ; breadth 27'6 JJL; breadth of isthmus 

 13 p.. 



SCOTLAND. South end of Scotston Moor, Aberdeen 

 (Roy ,\ Bissett). 



Geocjr. Distribution. Germany. 



We have not seen this small species, but from Reinsch's 

 figure, of which we give a copy, it seems quite distinctive. 

 Roy states that it was only once seen from its Scottish locality. 



72. Cosmarium arctoum Xordst. 

 (PI. LXIX, fig. 2.) 



Cosmarium arctoum Xordst. Desm. Arctose, 1875, p. 28, t. 7, f. 22; Desm. 



Gronland, 1885, p. 9; Freshw. Alg. N. Zeal. 1888, p. 61, t. 7, f. 29; 



De Toni, Syll. Alg. 1889, p. 944; Borg. Ferskv. Alg. Ostgronl. 1894, 



p. 20 ; Eoy & Biss. Scott. Desm. 1894, p. 42 ; Xordst. Index Desm. 1896, 



p. 50. 



C. arctoum a. typicum Eacib. Xonn. Desm. Poloii. 1885, p. 78. 

 Ursindla arctoa Kuntze, Eevis. gen. plant. 1891, p. 424. 



Cells very small, usually about 14- times longer than 



-ITT 



broad, in general outline subquadrate with rounded 

 angles and retuse sides ; constriction very slight ; 



