BRITISH DESMIDIACEjE. 



Length o2-o(j ILL ; breadth 24-25 ju ; breadth of 

 isthmus 9-11*5 /u ; thickness 8 ft. 

 ENGLAND.- -Penyghent, W. Yorks ! 



57. Cosmarium Nagelianum Breb. 

 (PI. LXVI, fig. 12.) 



Euastrum (Cosmarium) crenatum Nag. Gatt. eing. Alg. 1849, p. 120,, t. 7 A, 



f. 8 ; Gay, Monogr. loc. Conj. 1884, p. 61. 

 Cosmarium Nagelianum Breb. Liste Desm. 1856, p. 127 ; Arch, in Pritch. 



Infus. 1861, p. 732; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 164; 



Hansg. Prodi-. Algenfl. Bohm. 1888, p. 196; Kirclmer, Nachtr. Alg. 



Wiirtt. 1888, p. 154; De Toni, Syll. Alg. 1889, p. 942; Heimerl, 



Desm. Alp. 1891, p. 599; Gntw. Flor. glonow Galic. 1892, p. 126; 



Liitkem Desm. Attersees, 1893, p. 553 ; Schmidle, Beitr. Algenfl. 



Schwarzwald u. Eheineb. 1893, p. 30; Eoy & Biss. Scott. Desm. 1894, 



p. 169 ; Borg. Freshw. Alg. Faeroes, 1901, p. 227. 

 Ursinella Ndgeliana Knntze, Revis. gen. plant. 1891, p. 925. 



Cells small, about 1^ times longer than broad, very 

 deeply constricted, sinus narrowly linear ; semicells 

 truncate-pyramidate, basal angles rectangular or 

 obliquely truncate, sides with three undulations, upper 

 angles acute or subacute, apex straight or very slightly 

 biundulate. Vertical view elliptical. Cell- wall 

 sparsely punctate. 



Zy go spore . . . ? 



Length 26-30 ^ ; breadth 19-22*5 /u; breadth of 

 isthmus 6-8 /u ; thickness 10-? /n. 



SCOTLAND.- -Springhill near Aberdeen, and pool 

 near Loch Dawin, Aberdeen ; near Cowie, Kincardine 

 (Roy $ Bissett). 



IRELAND.- -Dublin and Wicklow (Archer). 



Geogr. Distribution.- -France. Germany. Austria. 

 G-alicia. Italy. Norway. Sweden. Faeroes. New 

 Zealand. Australia. E. Africa. United States. 

 Brazil. 



We have never examined any plants of this genus corre- 

 sponding exactly with Nagelr's figures of " Euastrum (Cos- 

 marium) crenatum" and we are in some doubt as to the exact 

 characters of the vertical view. The Desmid issued as " C. 

 Nagelianum Breb. forma ' in Nordstedt, Wittrock, and 

 Lagerheim, ' Alg. Exsic/ 1894., no. 1276, and determined by 

 Prof. W. Schmidle, we do not consider to belong to that 



