82 BRITISH DESM1D1ACEJE. 



Japan. Australia. E. Africa. Azores (form). United 

 States. 



C. abbreviatum Racib. is closely allied to C. sexangulare, 

 but is smaller and of different proportions. 



Forma minima Nordst. (PI. LXXII, figs. 4, 5.) 



C. sexangulare Lund, forma minima Nordst. in Botan. Notis. 1887, p. 162 ; 

 Freshw. Alg. N. Zeal. 1888, p. 60, t. 7, f. 26, 27 ; Gutw. Flor. Glon. 

 Okolic Lwowa, 1891, p. 46; Borge, Siissw. Chlor. Archang. 1894, p. 28, 

 t. 2, f . 29 ; Gutw. Flor. Glon. Okolic Tarnapola, 1894, p. 87 ; Xordst. 

 Index Desm. 1896, p. 233 ; G. S. West, Alg. Third Tanganyika Expedit. 

 1907, p. 119. 



About one third the size of the typical form, semi- 

 cells with the apex retuse and the upper lateral 

 margins conspicuously retuse. 



Length 13'5-15/x; breadth 11-12/x; breadth of 

 apices 5-8 p. ; breadth of isthmus 3 p.. 



SCOTLAND. Near Finstown, Orkneys ! 



Geogr. Distribution. - Russia. Poland. Central 

 Africa. Australia. New Zealand. Argentina. 



This form differs mostly in its minute size. The width of 

 the apex is very variable, and the superior lateral margins 

 are undoubtedly more retuse than in the typical form. It 

 should be compared with some of the small forms of C. 

 Regnellii. 



The Desmid figured by Borge (' Alg. Argentina u. Boliv.' 

 1906, p. 7, f. 2) as " C. granatum var. subangulare West 

 forma minor apicibus semicellularum latioribus' is without 

 doubt referable to C. sexangulare forma minima. On the 

 other hand, Bohlin ('Flor. Algol, d'eau douce d. A9ores/ 

 1901, p. 70, t. 1, f. 32) records and figures a form of C. 

 granatum Breb. under the name of C. sexangulare f. minima. 



103. Cosmarium pseudoprotuberans Kirchn. 

 (PL LXXII, figs. 6-8.) 



Cosmarium bioculatum Breb. forma Nordst. Desm. Spets. 1872, p. 29. 



C. pseudoprotuberans Kirchn. Alg. Scliles. 1878, p. 150; Nordst. Desm. 



Gronland, 1885, p. 8, t. 7, f . 3 ; De Toni, Syll. Alg. 1889, p. 951 ; ? Turn. 



Freshw. Alg. E. India, 1893, p. 59, t. 10, f . 6 ; ? Borg. Ferskv. Alg. 



Ostgronl. 1894, p. 18, t. 1, f. 12 ; Eoy & Biss. Scott. Desm. 189-1, p. 172 ; 



Johnson, Eare Desm. U. S. II, 1895, p. 293, t. 240, f . 24 ; Schmidle, Beitr. 



alp. Alg. 1895, p. 389 ; Nordst. Index Desm. 1896, p. 210 ; West & G-. S. 



West, New and Int. Freshw. Alg. 1896, p. 155, t. 4, f. 34; Alg. S. 



England, 1897, p. 486. 



C. pseudoprotuberans a. Kirchneri Eacib. Nonn. Desm. Polon. 1885, p. 82. 

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



