110 BRITISH DESMIDIACE^E. 



series. Cliloroplasts axile, one in each semicell, with 

 a central pyrenoid. 



Zygospore unknown. 



Length 28-32 p, ; breadth 20-21 /i. 



SCOTLAND.- -Birsemore Loch, Aberdeen (Roy fy 

 Bissetf). 



Geogr. Distribution.- -Finland. 



Messrs. Koy and Bissett record this species as " very rare ' 

 in the one locality in which they found it in Aherdeenshire. 

 The granules are stated by Elfving to be indistinct., and 

 Lagerheim lias described a form from Sweden (forma 

 depauperata) in which they are not present ; vide Lagerh. in 

 'Bot. Nbtiser/ 1886, p. 47. 



119. Cosmarium parvulum Breb. 

 (PL LXXIV, figs. 8-10.) 



Cosmarium parvulum Breb. Liste Desni. 1856, p. 133., t. 1, f. 18 ; Arch, in 

 Priteh. Iiifus. 1861, p. 735; Eabenh. Flor. Europ. Algar. Ill, 1868, 

 p. 177 ; Lund. Desm. Suec. 1871, p. 50 (forma) ; Nordst. Alg. aq. dale, 

 et Char. Saiidvic. 1878, p. 13; Gay, Monogr. loc, Coiij. 1884, p. 72; 

 Lagerh. Bidrag Amerik. Desm.-fl. 1885, p. 241 ; Cooke, Brit. Desm. 

 1887, p. 120, t, 43, f. 8 ; Boldt, Desmid. Gronland, 1888, p. 11 ; De Toni, 

 Syll. Alg. 1889, p. 958 ; Borge, Siissw. Chlor. Archang. 1894, p. 22 ; 

 Eoy & Biss. Scott. Desm. 1894, p. 170; Nordst. Index Desm. 1896, 

 p. 196 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 95 ; Alg. N. Ire- 

 land, 1902, p. 41. 



Ursinella parvula Knntze, Eevis. gen. plant. 1891, p. 925. 



Cosmarium obcuneatum West, Alg. W. Ireland, 1892, p. 162, t. 21, f. 18 ; 

 Alg. Engl. Lake Distr. 1892, p. 729, t. 9, f. 8 [forma] ; West & G. S. 

 West, Alg. S. England, 1897, p. 492. 



Dysphinctium parvulum (Breb.) Schmidle, Beitr. alp. Alg. 1895, p. 348. 



Cells small, 2-2-J- times longer than broad, very 

 slightly constricted, sinus a minute notch ; semicells 

 narrowly truncate-pyramiclate, sides commonly very 

 slightly convex, but sometimes straight or very slightly 

 concave, upper angles slightly rounded, apex truncate, 

 slightly convex, straight, or rarely very slightly con- 

 cave. Vertical view almost exactlv circular. Cell- 



u 



wall smooth, or delicately and irregularly punctate. 

 Cliloroplasts axile, one in each semicell, with a central 

 pyrenoicl and a number of small longitudinal ridges. 



Zygospore . ? 



Length 30-42 /JL ; breadth 14-1 7 p.; breadth of apex 

 7'5-9'5jLt; breadth of isthmus 13-14*5 /A. 



