54 BRITISH DESMIDIACEJE. 



tricrenate- dentate. Cell- wall very finely punctate. 

 Chloroplast axile with two pyrenoids. 



Zygospore unknown. 



Length 40-44 ^ ; breadth 35-45 IJL ; breadth of 

 isthmus 12-1 7 /A; thickness 24-26 /x. 



r. Distribution.- -New Zealand. W. Africa. 



The typical form is not known to occur in the British 

 Islands. 



Forma minor West & G. S. West. (PL LXIX, figs. 



31, 32.) 



Cosmarium odontopleurum Arch, in Boy & Biss. Scott. Desm. 1894, p. 169, 



t. 2, f. 13 ; Nordst. Index Desm. 1896, p. 188. 

 C. repandum Xordst. forma minor West & G. S. West, Some Desm. U. S. 



1898, p. 303. 



Cells half or less than half the size of the type, with 

 the three crenations absent from the oblique view of 

 the basal angles. 



Zygospore globose and smooth. 



Length 15-22 ^ ; breath 14-20 u ; breadth of isthmus 

 5 "5-8 in ; diam. zygosp. 30 /a. 



SCOTLAND.- -Powlair, Aboyne ; Homehead, Aberdeen 

 (Boy $ Sissett). 



IRELAND.- -Dublin and Wicklow (Archer). 



Geogr. Distribution. United States. 



79. Cosmarium rectangulare Grim. 

 (PL LXX, figs. 1, 2.) 



Cosmarium rectangulare Grim, in Eabenh. Flor. Europ. Algar. Ill, 1868, 

 . p. 166 ; De Torn, Syll. Alg. 1889, p. 987 ; West, Alg-. W. Ireland, 1892, 



p. 146 ; Alg. Engl. Lake Distr. 1892, p. 725 ; Gutw. Flor. glonow Galic. 



1892, p. 129; Flor. Glon. Okolic Tarnopola, 1894, p. 92 ; Eoy & Biss. 



Scott, Desm. 1894, p. 173 ; West & G. S. West, Alg-. S. England, 1897, 



p. 486 ; Some Desm. U. S. 1898, p. 302 ; Alga-fl. Yorks. 1900, p. 91 ; Alg. 



X. Ireland, 1902, p. 34. 

 Cosmarium gotlandicnm Wittr. Gotl. ()l. sotv. Alg. 1872, p. 60, t. 4, f. 14 ; 



Xordst. Norges Desm. 1873, p. 19 ; Cooke, Brit. Desm. 1886, p. 88, t. 37, 



f. 4; West, Alg. X. Wales, 1890, p. 288; Johns. Eare Desm. U. S. II, 



1895, p. 293, t. 240, f. 26. 

 Ursinella rectangularis Ivuntze, Eevis. gen. plant. 1891, p. 925. 



Cells of medium size, about 1J times as long as 



