MICEASTEEIAS. 97 



name which the author gave to Echinella radiosa Lyngbye. 

 Micrasterias radiosa Ralfs (' Brit, Desm/ 1848, p. 72, t. 8, f. 3) 

 which that author wrongly attributed to Agardh, is the 

 first good account of the Desmid described and figured by 

 Ehrenberg five years previously (1843) under the name of 

 " Euastrum Sol. 3 ' Ralfs himself recognized this identity and 

 placed Euastrum Sol Ehrenb. as a synonym of his Micras- 

 terias radiosa. The specific name "Sol" must therefore take 

 precedence over Ralfs' name "radiosa." 



Micrasterias Sol is almost circular in outline, and is easily 

 distinguished by the depth and elegance of its lobulation. 

 The margins of the deeper incisions are usually slightly 

 undulate and the lobules frequently overlap. 



North American specimens of this species exhibit much 

 greater variation than is shown in British examples. 



Var. ornata Nordst, (PI. XL VI, figs. 3, 4.) 



Micrasterias radiosa Ralfs var. ornata Xordst. Desm. Brasil, 1870, p. 223, 

 t. 2, f. 11 ; Lund. Desm. Suec. 1871, p. 13 ; Roy & Biss. Scott. Desm. 

 1893, p. 174 ; West & G-. S. West, Some N". Amer. Desm. 1896, p. 240. 



M. Sol (Ehrenb.) Kiitz. var. ornata Nordst. in Pointsfor. Skand. Vaxt. iv, 

 1880, p. 25. 



AVith a row of minute teeth or deiiticulations on 

 each side of the sinus and of the incisions between the 

 five lobes of the semicells. 



Length 112-188 p.; breadth 110-171 /A; breadth of 

 isthmus 16-18 ^', thickness 22 p.. 



WALES. Capel Curig, Carnarvonshire ! 



SCOTLAND. Near Brin, Inverness; Slewdrum and 

 near Craigendinnie Farm, Aberdeen; Scolty Dam, 

 Kincardine (Roy fy Bissett}. Plankton of Loch Doon, 

 Ayrshire ! Plankton of Loch Fadaghoda, Lewis, Outer 

 Hebrides ! 



Geogr. Distribution. Norway. United States. 

 Brazil. 



10. Micrasterias apiculata (Ehrenb.) Menegh. 

 (PI. XL VII, figs. 1, 2.) 



Euastrum apiculatum Ehrenb., 1834 ; Infus. 1838, p. 161, t. 12, f . II. 

 Micrasterias apiculata (Ehrenb.) Menegh. Synops. Desm. 1840, p. 216; 



VOL. II. 



