190 BRITISH DESMIDIACEJE. 



Length 28*5 JJL ; breadth 25-27 /x ; breadth of isth- 

 mus 9 '5 fji. 



SCOTLAND.- -Plankton of Loch Asta, Shetlands ! 



IRELAND.- -Plankton of Lough Neagh ! Lough 

 Gartan, Donegal ! 



In tliis form some or all of the angles are furnished with 

 two minute spines. The form thus approaches the granulate 

 forms of St. Avicnla, and to a smaller extent it resembles St. 

 denticulatum. 



Var. acutum (Breb.) W. & G. S. West, (PL CXXVIII, 



fig. 14.) 



Staurastrum acutum Breb. Liste Desm. 1856, p. 143, t. 1, f. 26; Eabenh. 



Flor. Europ. Alg. Ill, 1868, p. 202; Kirchn. Alg. Schles. 1878, p. 168; 



Roy & Biss. Scott. Desm. 1893, p. 178. 

 St. gramdosum var. acutum (Breb.) W. & G. S. West, Alg. N. Ireland, 



1902, p. 45, t. 2, f . 25 ; Scott. Fresliw. Plankton, I. 1903, p. 529 ; Brit. 



Freshw. Phytoplankton, etc., 1909, p. 182. 



Semicells elliptic-fusiform, dorsal and ventral margins 

 more equally convex ; sides of vertical view straight. 



Length 29-30 p, ; breadth without mucro 28-31 //,, 

 with mucro 30-33 ^ ; breadth of isthmus 1 1 '5-12-5 p.. 



WALES.- -Capel Curig, Carnarvonshire (Rot/). 



SCOTLAND.- -Ross, Inverness, Aberdeen, Kincardine, 

 Forfar, Perth (Roy Bissett). Plankton of Loch 

 Mhor Bharabhais in Lewis, Outer Hebrides ! 



ICELAND.- -Near Glenties, Donegal ! Plankton of 

 Loug-h Neao'h ! Plankton of Lower River Barm, Lon- 



o o 



donderry ! 



Geocjr. Distribution.- -France. Germany. 



40. Staurastrum paxilliferum G-. S. West. 

 (PI. CXXVIII, fig. 15.) 



Stattrastrum paxillifet-um, G. S. West, Alga-fl. Cambr. 1899, p. 219, t. 396, 

 f . 8 ; W. & Gr. S. West, Alga-fl. Yorks. 1900, p. 100. 



Cells somewhat small, a little longer than broad, 

 deeply constricted, sinus open and subrectangular, 

 with a submamillate apex ; semicells subelliptic, ven- 

 tral margin a little more convex than the dorsal 

 margin, angles subacute and furnished with a prominent 



