158 BRITISH DESMIDIACEJE. 



Var. depressum Roy & Biss. (PI. CXXIV, 



figs. 17-19.) 



St. orbiculare var. depressum Roy & Biss. Jap. Desm. 1886, p. 237, t. 268, 

 f . 14 ; Nordst. Freshw. Alg. N. Zeal. 1888, p. 42 ; West, Alg. W. Ireland, 

 1892, p. 177 ; Alg. Engl. Lake Distr. 1892, p. 731 ; W. & G-. S. West, 

 Alg. S. England, 1897, p. 494 ; Alga-fl. Yorks. 1900, p. 100 ; Freshw. 

 Chlorophy. Koh Chang, 1901, p. 178; Alg. N. Ireland, 1902, p. 49; 

 Freshw. Alg. Orkneys and Shetlands, 1905, p. 25 ; Brit. Freshw. Phyto- 

 plankton, etc., p. 182. 



Cells small, as long as broad, semicells much 

 depressed ; cell-wall smooth. 



Length 22-27 ft; breadth 20-27 /x; breadth of 

 isthmus 67'5/i,. 



ENGLAND.- -Near Bowness, Westmoreland ! Hawks- 

 head, Lancashire ! Malham Tarn and near Clapham, 

 W. Yorks ! Pilmoor and Strensall, N. Yorks ! Riccall 

 and Skip with Commons, E. Yorks ! Dernford Fen 

 and "Wicken Fen, Cambridge ! Chobham and Witley 

 Commons, Surrey ! New Forest, Hants ! Near 

 the Lizard, Cornwall ! 



WALES.- -Llyn Idwal and Y Foel Fras, Carnarvon- 

 shire ! Brecon ! 



SCOTLAND.- -Rhiconich, Sutherland ! At 3500ft. on 

 Loclmagar, Aberdeen ! Ben Laoigh, Perth ! Tents 

 Moor, Fife (Roy <$ Blssett). Renfrew ! Near Loch 

 Doon, Avr ! Orkneys and Shetlands, in both the boe'S 



tj tf t_j 



and the plankton ! 



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

 Londonderry ! 



Geogr. Distribution.- -Qakici& in Austria. Sweden. 

 N. Russia. Central China. Japan. Siam. Australia, 

 New Zealand. Madagascar. 



Var. extensum Nordst. (PL CXXV, figs. 1, 2.) 



St. orbiculare var. extensum Nordst. Norges Desm. 1873, p. 26, t. 1, f. 10 ; 

 Desm. Ital. 1876, p. 42 ; West, Alg. Eng. Lake Distr. 1892, p. 731 ; 

 Notes Alg. II, 1900, p. 296, t. 412, f. 19 ; Alga-fl. Yorks, 1900, p. 100. 



Cells 1-i- times as lono- as broad; semicells relatively 



o t> 



higher and more inflated. 



Zygospores exactly similar to those of var. Ralfsii. 



