COSMARIUM. 123 



and nearer C. Blyttii Wille. It differs from the latter species 

 chiefly in its smooth cell-wall, and to some extent in the lower 

 parts of the sides of the semicells. 



132. Cosmarium zonatum Lund. 

 (PI. LXXVII, figs. 20, 2L) 



Cosmarium zonatum Lund. Desm. Suec. 1871, p. 50, t. 3, f. 18 ; Liitkeui. 



Desm. Attersees, 1893, p. 551 ; Nordst. Index Desm. 1896, p. 273 ; 



Schmidle, Lappmark Siisswasseralgen, 1898, p. 25 ; West & Gr. S. West, 



Freshw. Alg. Ceylon, 1902, p. 163. 

 Dysphinctium zonatum (Lund.) De Toni, Syll. Alg. 1889, p. 883. 



Cells rather small, twice as long as broad, deeply 

 constricted, sinus open and acute-angled; semicells 

 subovate, gradually attenuated from a strongly convex 

 base to a convex apex, sides slightly retuse. Side 

 view of semicell ovate. Vertical view elliptic-circular. 

 Cell-wall slightly thickened in the middle of each 

 apex, smooth except for definite zones of punctula- 

 tions ; a simple series of punctulations immediately 

 below each apex, one just above the middle of the 

 semicells, a double series across the basal (widest) 

 part of the semicells, and a few punctulations at the 

 extreme base. Chloroplasts axile, one in each semi- 

 cell, with a central pyrenoid. 



Zygospore unknown. 



Length 43*5-51 /x; breadth 22-26 /x; breadth of 

 isthmus 7*5-11 /x; thickness 20-21 /x. 



SCOTLAND.- -Bhicoirich, Sutherland ! 



Geogr. Distribution. --Sweden. Austria. Ceylon. 

 E. Africa (form). 



This rare species is well characterized by the outward 

 form of its cells and the zones (annular series) of delicate 

 punctulations. 



133. Cosmarium binerve Lund. 

 (PI. LXXVII, fig. 22.) 



? Cosmarium quadratum Hass. Brit. Fresliw. Alg. 1845, p. 367, t. 86, 



f. 12. 

 C. binerve Lund. Desm. Siiec. 1871, p. 49, t. 3, f. 15 ; Nordst. Index Desin. 



1896, p. 61. 

 DyspMnctium binerve (Limd.) De Toni, Syll. Alg. 1891, p. 924. 



