COSMARIUM. 177 



SCOTLAND .- -Sutherland ! , Ross, Inverness!, Aber- 

 deen, Perth ! (Roy Bissetf). Lewis and Harris, 

 Outer Hebrides ! Orkneys ! Shetlands ! Not uncommon 

 in the plankton ! 



IRELAND.- -Donegal ! Mayo ! Galway ! Kerry ! Dub- 

 lin and Wicklow (Archer). Londonderry ! 



Geor/r. Distribution.- -Grermsinj. Galicia in Austria. 

 Italy. Faeroes. Greenland. India. Ceylon. Burmah. 

 New Zealand (var.). Australia. Abyssinia. United 

 States. 



There appears to be no doubt of the almost strict identity 

 of " Euastrum depression Nag." (1849) and "Cosmarium 

 Scenedesmus Delp." (1877). Lundell first pointed out the 

 affinities of this Desmid, and also placed it under the genus 

 Cosmarium as C. depressum Nag. (Lund.). 



C. depressum is distinguished from C. Plutseolus by its 

 proportionately greater breadth, by its depressed- elliptic 

 semicells (not reniform), and by the absence of a central 

 protuberance. It also bears a great resemblance to Arthro- 

 desmus convergens Ehrenb. without the spines, and Jacobsen 

 actually referred it to this species as "var. inermis." 



Var. achondrum (Boldt) West & G. S. West. (PI. 



LXII, figs. 6-9.) 



C. Phaseolus Breb. var. achondrum Boldt, Sibir. Chloropliy. 1885, p. 103, 



t. 5, f . 7 ; De Toni, Syll. Alg. 1889, p. 1002 ; Sclimidle, Beitr. Algenfl. 



Sch-warzwald. n. Rheineb. 1893, p. 102, t. 5, f. 11 ; Berg. FresliAv. Alg. 



OstgrSnl. 1894, p. 19, t, 1, f. 13 ; Roy & Biss. Scott. Desm. 1894, p. 171. 

 C. depressum (Nag.) Lund. var. achondrum (Boldt) West & Gr. S. West. 



Further Contrib. Freslrvv. Plankton Scott. Lochs, 1905, p. 484. 



Cells as long as broad, or nearly so ; semicells sub- 

 hexagonal-elliptic, apex broader and more truncate. 



Length 37-51 A*; breadth 40-51 /m ; breadth of isth- 

 mus 12-17 / ; thickness 22-23 p. 



EXGLAXD. Malham Tarn, W. Yorks ! 



WALES.- -Capel Curig Lakes, Carnarvonshire! 



SCOTLAND.- -Near Loch Coruisk in Skye, Inverness 

 (Roy ft Bissetf). Mull in Argyll (Borge). General in 

 the plankton of the mainland and the Outer Hebrides ! 



IEELAXD.- -Lough Gartan, Donegal ! Lakes between 

 Clif den and Roundstone, Gal way ! 



VOL. II. 12 



