COSMARIUM. 33 



variety. We have already commented upon the tendency 

 towards the formation of a similar basal /one in certain forms 

 of C. amoenum. 



239. Cosmarium latifrons Lund. 



(PI. XCIV, fig. 6.) 



Cosmarium latifrons Lund. Desm. Suec. 1871, p. 30, t. 3, f. 7 ; De Toni, 

 Syll. Alg. 1889, p. lull ; Roy & Biss. Scott. Desm. 1894, p. 104 ; Nordst, 

 Index Desmid. 1896, p. 15(5. 



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



Cells small, as long as broad, moderately constricted, 

 sinus very narrow and linear ; semicells widely trapezi- 

 form, sides upwardly diverging from a broad base, 

 inferior angles obtuse-angled, superior angles slightly 

 rounded, apex wide and convex ; cell-wall finely 

 granulate except in the centre of each semicell, the 

 margin having a finely serrate appearance, in the 

 centre with a small protuberance furnished with three 

 vertical series of larger granules. Side view of semi- 

 cell ovate, with a granulate inflation near the base on 

 each side. Vertical view elliptic, with a small tri- 

 granulate inflation at the middle on each side, granulate 

 except for an elliptic, smooth area in the centre. Chloro- 

 plasts axile, with one pyrenoid in each semicell. 



Zygospore unknown. 



Length 34-38 /x ; breadth 34-38 p ; breadth of 

 isthmus 1-5 JLC ; thickness 23*3 p.. 



SCOTLAND.- -Barrelwell Moss near Brechin, Forfar 

 (Roy $ Bissett). 



Geoqr. Distribution. Galicia in Austria. Norway. 



>J v 



Sweden. N. Russia (a form). Siberia. 



C. latifrons is a small species somewhat resembling certain 

 forms of C. Itu-fhun in external shape, bnt with very distinctive 

 characters. 



240. Cosmarium lepidum West. 



(PI. XCIV, fig. 10.) 



Cosmarium lepidum West, Alg. N. Yorks. 1889, p. 292, t. 291, f. 14 ; Eoy 

 & Biss. Scott. Desni. 1894, p. 105 ; Nordst. Index Desm. 1896, p. 157 ; W. 

 & G. S. West, Alga-fl. Yorks. 1900, p. 89. 



VOL. IV. 3 



