114 BRITISH DESMIDIACE^. 



concave, with a series of projecting emarginate spines, 

 and a further row of spines just within the margin ; angles 

 produced into granulate processes. 



Zygospore unknown. 



Length about 51 [JL ; breadth, including processes y 

 about 60 [Ji ; breadth of isthmus 12 pi. 



ENGLAND. Pilmoor, N. Yorks ! Thurslev Common. 



/ 



Surrey ! 



Geogr. Distribution.- - C4ermany (var.). Galicia in 

 Austria. Norway. Poland. N. Russia. Faeroes. Green- 

 land. Siberia (var.). India. New Zealand (var.). United 

 States. 



St. Pseudosebaldi differs from St. Manfeldtii in the distant 

 granules at the base of the semicell, and in the spiny lateral 

 margins in the end view. From St. Sebaldi var. ornatum it is- 

 distinguished by its shorter processes and the bifid spines which 

 project from the lateral margins in the end view. 



Var. simplicius West. (PL CXLIX, fig. 13.) 



St. Pseudosebaldi var. simplicius West, Alg. Engl. Lake Distr. 1892, p. 21, 

 t. 9, f. 37. 



Cells smaller than in the type, with the apical spines 

 simple instead of emarginate ; processes shorter, tipped 

 with 3 spines longer than usual. 



Length, with spines, 32 [i ; breadth 46 pi ; breadth of 

 isthmus 9 \i . 



ENGLAND. Brandreth, Westmoreland ! 



120. Staurastrum Manfeldtii Delp. 

 (PL CXLVIII, fig. 2.) 



Staurastrum Manfeldtii Delp. Spec. Desm. subalp. 1877, p. 160, t. 13,. 

 f. 6-19 ; De Toni, Syll. Alg. 1889, p. 1214 ; Gutw. Flor. Glon. Okolic 

 Tarnapola, 1894, p. 108 : Llitkem. Desm. Central China, 1900, p. 123 ; 

 Comere, Desm. de France, 1901, p. 158, t, 11, f. 8 ; West & G. S. West. 

 Alg. N. Ireland, 1902, p. 56 ; Freshw. Alg. Orkneys & Shetlands, 1905 y 

 p. 27 ; Brit, Freshw. Phytoplankton, 1909, p. 175 ; Hustedt, Desm. et 

 Bacill. Tirol. 1911, p. 339. 



Cells of medium size, about Ij times broader than 

 long, including the processes ; constriction small ; semi- 



