rOSMAIHUM. 197 



angles. The latter may even be slightly produced as in 

 fig. 28, PL LXIII. Although originally described as a 

 variety of C. pachydermum, we do not think it has any close 

 nflinity with that species, the outward form of the semicells 

 1 icing so very different. 



46. Cosmarium nitidulum De Not. 

 (PL LXIV, figs. 1-3.) 



Cosmarium nitidulum De Not. Desm. Ital. 1867, p. 42, t. 3, f. 26 ; Rabenh. 



Flor. Em-op. Algar. Ill, 1868, p. 169; Lund. Desm. Suec. 1871, p. 35; 



Wolle, Desm. U.S. 1884, p. 62, t. 18, f . 18, t. 52, f. 9-10 ; Hansg. Prodr. 



Algenfl. Bohm. 1888, p. 194 ; Nordst. Preshw. Alg. N. Zeal. 1888, p. 59, 



t. 6, f. 17 ; De Toni, Syll. Alg. 1889, p. 935 ; West, Alg. N. Wales, 1890, 



p. 288 ; Alg-. W. Ireland, 1892, p. 145 ; Alg. Eng. Lake Distr. 1892, 



p. 725 ; Roy & Biss. Scott. Desm. 1894, p. 169 ; Nordst. Index Desm. 



1896, p. 181 ; West & G. S. West, Alg. S. England, 1897, p. 485 ; Alga-fl. 



Yorks. 1900, p. 78. 

 Euastrum (Cosmarium) nitidulum Gay forma genuina Gay, Monogr. loc. 



Conj. 1884, p. 59. 

 Cosmarium nitidulum De Not. f. punctulata Gutw. Flor. glon. Galic. 2, 



1890, p. 14, t. 1, f. 11. 



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

 ? Cosmarium rectosporum Turn. Freshw. Alg. E. India, 1893, p. 69, t. 10, 



f. 16. 



Cells of moderate size, a little longer than broad, 

 deeply constricted, sinus very narrowly linear with a 

 slightly-dilated extremity ; semicells truncate-subsemi- 

 circular, basal angles broadly rounded, sides convex 

 and converging upwards, upper angles slightly rounded, 

 apex small, truncate-convex, straight, or slightly retuse. 

 Side view of semicell subcircular. Vertical view 

 elliptic. Cell-wall very minutely punctate (punctula- 

 tions often scarcely visible). Chloroplasts axile, each 

 with one pyrenoid. 



Zygospore unknown. 



Length 30-41 //, ; breadth 23-33 p, ; breadth of 

 isthmus 8-10 /*, ; thickness 16-22 '5 p.. 



ENGLAND. Cullingworth, W. Yorks ! Mickle Fell, 

 Pilmoor, and near Bees Cliff, N. Yorks ! Leicester- 

 shire (Roy). Thursley Common, Surrey! 



WALES. Capel Curig (CooJce fy Wills') and Bethesda!, 

 Carnarvonshire. 



SCOTLAND.- -Heughhead near Aboyne, and foot of 



