24 BRITISH DESMIDIACE^:. 



Zygospore spherical, with a limited number of long 

 stout spines, swollen at the base. 



Length, without spines, 20-31 JJL ; breadth, without 

 spines, 18-28(jt ; breadth of isthmus 5-7 [i ; length of 

 spines 5-12{ji; diam. zygosp., without spines, 25 (JL ; 

 including spines 55 [z. 



ENGLAND. - - Cumberland ! Westmoreland (Biss.) 

 Lancashire ! W., N., and E. Yorks ! Essex ! Oxford- 

 shire ! Plankton of Bracebridge Pool, Button Park, 

 Warwicks! Berks (Griffiths). Surrey! Kent! Hants- 

 (Rolfs] ; zygospores from New Forest ! Devonshire 

 (Harris) ! Cornwall ! 



WALES. Capel Curig (Cooke & Wills) ! Bettws-y-coed 

 and Glyder Fawr (Roy), Dolbadarn Castle and Llyn 

 Ogwen, Carnarvonshire ! Ffestiniog, Merioneth ! 



SCOTLAND.- -Ross, Inverness, Banff, Aberdeen, Kin- 

 cardine, Forfar, Perth and Argyle (Roy & Biss.). Mull 

 (Borge). Orkneys and Shetlands ! 



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

 Plankton of Lough Neagh ! Dublin and Wicklow (Arch . ) . 



Geogr. Distribution.- -France. Germany. Switzerland. 

 Austria and Galicia. Hungary. Roumania. Italy. 

 Norway. Sweden. Denmark. Bornholm. Finland. 

 Poland. N. and S. Russia. Faeroes. Greenland. 

 Siberia. Japan. Ceylon. Burma. Australia. New 

 Zealand. Abyssinia. Central Africa. Nova Scotia. 

 United States. Canada. Brazil. 



St. cuspidatum is an extremely common and very widely dis- 

 tributed species, and its elongated isthmus is one of its most 

 characteristic features. The spines usually converge slightly 

 towards those of the other semicell. 



Var. maximum West, (PL CXXXII, figs. 18, 19.) 



Staurastrum cuspidatuni var. maximum West, Add. Alg. W. Yorks. II, 

 1891, p. 247 ; Alg. Engl. Lake Distr. 1892, p. 18 ; West & G. S. West, 

 Alg. S. England, 1897, p. 492 ; Schmidle, Lappmark Susswasseralgen, 

 1898, p. 49, t. 2, f. 33 ; West & G. S. West, Alga-fl. Yorks. 1902, p. 97 ; 

 Scott. Freshw. Plankton, 1, 1903, p. 545, 1. 17, f. 13 ; Freshw. Alg. Orkneys 

 and Shetlands, 1905, p. 24 ; Further Contrib. Freshw. Plankton Scott. 

 Lochs, 1905, p. 486, t, 1, 5 ; Period. Phytoplankton Brit. Lakes, 1912, 

 p. 414. 



