24 BRITISH DESMIDIACE^. 



Length 58-65 /x ; breadth 37-42 //, ; breadth of 

 isthmus 11 '5-1 3 p. ; thickness 24-25 p.. 



WALES. Capel Curig, and Llyn-y-cwm-ffynon, Car- 

 narvonshire ! 



SCOTLAND. On Ben Mulch Dhui, near Loch Etcha- 

 chan, Aberdeen (Roy fy Bissett). 



Geogr . Dis trib i itioi i . Finlan d . 



E. aboense differs from E. inerme in its slightly larger size, 

 in the relatively greater width of the semicells, in the rounded 

 basal angles, and in the scrobiculations on the front of the 

 semicells. The small thickened protuberance which is situated 

 just above the isthmus in the semicells of E. inerme, is repre- 

 sented by a very slight protuberance in E. aboense. The side 

 and vertical views also differ slightly. It is a species rarely 

 met with. 



12. Euastrum inerme (Ralfs) Lund. 

 (PL XXXVI, figs. 7, 8.) 



Euastrum elegans j3 inerme Kalfs, Brit. Desm. 1848, p. 89, t. 14, f . 7 e ; 



Eabenh. Flor. Eiirop. Algar. Ill, 1868, p. 186 ; Kirchn. Alg. Schles. 



1878, p. 159 ; Hausg. Prodr. Algenfl. Bohm. 1888, p. 207. 

 Euastrum inerme Lund. Desm. Suec. 1871, p. 20, t. 2, f . 3 ; Cooke, Brit. 



Desm. 1886, p. 75, t. 35, f . 4 ; De Toni, Syll. Alg. 1889, p. 1103 ; West, 



Alg. W. Ireland, 1892, p. 139 ; Eoy & Biss. Scott. Desm. 1893, p. 177 ; 



Nordst. Index Desm. 1896, p. 146 ; West & G. S. West, Alg. S. England, 



1897, p. 484 ; Alg. N. Ireland, 1902, p. 29. 

 E. inerme a. Ralfsii Racib. Nonn. Desm. Polon. 1885, p. 92. 

 E. inerme c. Lundellii Kacib. I.e. 

 Helierella inermis Kuntze, Eevis. gen. plant. 1891, p. 898. 



Cells small, subelliptic in outline, about If times 

 longer than broad, very deeply constricted, sinus nar- 

 rowly linear with a slightly-dilated extremity ; semi- 

 cells subpyramidate, basal angles obliquely truncate so 

 that the widest part of the semicell is above the base ; 

 lateral margins with two slight hollows, having a broad, 

 rounded projection between ; apex slightly protracted, 

 truncate, with a deep and narrow median notch; semi- 

 cells with a small thickened protuberance in the middle 

 immediately above the isthmus, having two small pro- 

 tuberances across the centre and a large scrobiculation 

 between them. Side view of semicell pyramidate with 

 a subquadrate base ; lateral margins slightly retuse 



