172 BRITISH DESM1DIACE.E. 



0. Jacobsenii Roy in Biss. Desni. Windermere, 188-4, p. 194 ; Cooke, Brit. 

 Desm. 1887, p. 120, t. 43, f. 3 ; Nordst. Bornli. Desm. 1888, p. 200 ; Roy 

 & Biss. Scott. Desm. 1894, p. 168. 



Cells almost 1^ times as long as broad, sinus open 

 but rounded at the apex; semicells more equally 

 elliptic or oblong-elliptic. 



Length 28-45 /A ; breadth 18-27 /n; breadth of isth- 

 mus 4* 5-7 *5 yu. 



ENGLAND. Near Bowness, Westmoreland (Bissett). 



SCOTLAND. Slewdrum, Presswhin, Logie-Coldstone, 

 and Grlen Clunie, Aberdeen ; Crathes, and Dalbrake in 

 Strachan, Kincardine (Roy $' Bissett). 



Geogr. Distribution.- -Germany. Gralicia in Austria. 

 Norway. Sweden. Denmark. Bornholm. Central 

 Africa. 



This form is of the same relative length and breadth as 

 typical (7. contraction, but differs in the more regularly elliptic 

 semicells. It is scarcely to be separated from it. 



Var. ellipsoideum (Elfv.) West & G. S. West. 

 (PI. LXI, figs. 28, 35.) 



Cosmarium ellipsoideum Elfv. Anteck. Finska Desm. 1881, p. 13, t. 1,'f. 10; 



De Toni, Syll. Alg. 1889, p. 953 ; West & G. S. West, Alg. S. England, 



1897, p. 491. 



Ursinella ellipsoidea Kuntze, Revis. gen. plant. 1891, p. 924. 

 Cosmarium contraction Kirchii. var. ellipsoideum (Elfv.) West & G. S. 



West, Alg. N. Ireland, 1902, p. 40. 



Cells shorter, not more than 1J times as long as 

 broad, semicells more exactly elliptic, although the apex 

 is sometimes slightly flattened in the middle. Cell-wall 

 usually smooth. 



Zygospore globose and smooth. 



Length 31-51 //, ; breadth 24-42 ^ ; breadth of 

 isthmus 7-12/x; thickness 14* 5-2 7 JJL; diam. zygosp. 

 29-36 p.. 



ENGLAND.- -Thursley Common, Surrey ! 



W AL K s .- -C ap el C urig, C am arvon shire ! 



SCOTLAND.- -Skye, and also plankton of Loch Bair- 

 ness, Inverness ! Plankton of Lochs Langabhat, 

 an Tomain, and Stranabhat, Lewis, and of Lochs 



