244 BRITISH DESMIDIACE^E. 



Filaments flattened and not twisted, cells in vertical 

 view oblong with rounded poles, and sides slightly 

 concave. 



Length 14-19 pi; breadth 25-32'5 pt : breadth of 

 isthmus 22-24 [ji ; breadth of apices 19-28 pi. 



ENGLAND. Strensall Common, N. Yorks ! 



SCOTLAND.- -Rare. Pools near Birsemoor Loch, Aber- 

 deen ; near Banchory, Kincardine (Roy & Biss.). 



Geogr. Distribution. France. Germany. Italy. 

 Sweden. Denmark. United States. 



Var. acutius Nordst. (PL CLXIV, fig. 6.) 



Desmidium Aptogonum var. acutius Nordst. Alg. Sandvic. 1878, p. 11, 

 t. 1, f. 21, 22; De Toni, Syll. Alg. 1889, p. 782; West, Alg. Engl. 

 Lake Distr. 1892, p. 7 ; West & G. S. West, Alga-fl. Yorks. 1902, p. 110 ; 

 Hirn, Desm. Finnland, 1903, p. 14. 



Lateral angles in the front view not broadly rounded, 

 but slightly retuse in the upper part, so that a subacute 

 angle points towards the apex of the semicell ; in other 

 respects similar to the type ; triangular or quadrangular 

 in the vertical view. 



Length 16-23^; breadth 32-43 pi ; breadth of 

 isthmus 26-34 [JL ; breadth of apices 26-34 \i. 



ENGLAND. Bowness, Westmoreland ! Pilmoor, N. 

 Yorks ! 



Geogr. Distribution. Galicia in Austria. Finland. 

 Java. Australia. Sandwich Isles. United States. 



2. Desmidium pseudostreptonema W. & G. S. West. 



(PL CLXV, figs. 5, 6.) 



Desmidium pseudostreptonema West & G. S. West, Alg. Ceylon, 1902, p. 193, 

 t. 22, f. 35-37 ; Compar. Study Plankton Irish Lakes, 1906, p. 104, t. 11, 

 f. 23. 



Cells of medium size, somewhat compressed, 1^-2 

 times broader than long, deeply constricted, sinus 

 narrow, gradually inflated very slightly towards the 

 apex ; semicells transversely and narrowly oblong, 

 sides rounded, apex rather convex, with short connect- 



