146 BRITISH DESMIDIACE^E. 



Stranabhat and an Tomain, Lewis, Lochs Diracleet and 

 Laxadale, Harris, Outer Hebrides ! 



IRELAND.- -Lough Guitane, and in the plankton, 

 Kerry ! Plankton of Lough Neagh ! 



St. anatinum var. truncatum is more frequent in plankton 

 than in any other hahitat. 



Var. pelagicum W. & G. S. West. (PL CXLVII, fig. 3.) 



St. anatinum var. pelagicum West & G. S. W^est, Alg. N. Ireland, 1902, 

 p. 55, t. 1, f. 26 ; Scott. Freshw. Plankton, I, 1903, p. 530 ; Further 

 Contrib. Plankton Scott. Lochs, 1905, p. 487. 



Cells smaller than in the type, semicells relatively 

 longer (excluding the processes) and more cup-shaped ; 

 processes slightly narrower. 



Length, without processes, 40-46 \L ; with processes, 

 57-65 \L ; breadth, with processes, 65-77 \L ; breadth of 

 isthmus 11*5-1 2' 5 [L. 



SCOTLAND. Plankton of Loch Shin, Sutherland ! ; of 

 Lochs na Criche and Shiel, Inverness ! ; and of Loch Mor 

 Bharabhais, Lewis, Outer Hebrides ! 



IRELAND.- -Plankton of Lough Beg, Londonderry ! 



This variety occurs exclusively in plankton, and is readily 

 distinguished from the type by its smaller size, by the different 

 shape of the semicells, and by the narrower and more delicate 

 processes. The granulation is similar to that of the type. 



Var. longibrachiatum W. & G. S. West. (PI. CXLVII, 



fig. 5.) 



St. anatinum var. longibrachiatum West & G. S. West, Further Contrib. 

 Freshw. Plankton Scott. Lochs, 1905, p. 504, t. 7, f. 8, 9. 



Body of semicell practically smooth beneath the apical 

 row of verrucae ; processes much longer than in the 

 type, tapering gradually to the apices. Lateral margins 

 in end view undulate but not verrucose, with a series 

 of verrucse just within the margin as in the type. 



Length, without processes, 37 ^ ; breadth, without 

 processes, about 29^; with processes, 110-131 (Ji ; 

 breadth of isthmus 11*5 i. 



