264 BRITISH DESMIDIACE.E. 



Closterium pronum Breb. (vol. i, p. 173). 

 Forma brevius West. 



Cl. promt ni i. brevius West, Clare Isl. Alg. 1912, p. 13. 



Cells always distinctly shorter. 

 Length 222-250 \L ; breadth 8*4-9 u. 

 IRELAND. Clare Isle, Mayo ! 



Genus EUASTRUM Ehrenb. 



Euastrum laticolle West. 

 (PL CLXVI, fig. 3.) 



Euastrum laticolle U. 8. West in Journ. Bot. 1912, p. 89. 



Cells of medium size, about li times longer than 



' o o 



broad, very deeply constricted, sinus extremely narrow 

 and linear ; semicells 3-lobed, lobes separated by broad 

 and shallow concavities ; lateral lobes trapeziform with 

 the upper and lower angles gently rounded, sides di- 

 verging upwards and slightly concave ; polar lobe 

 transversely subrectangular, angles scarcely rounded 

 and slightly produced, apex convex, but retuse in the 

 middle ; with a small swelling in the middle of the semi- 

 cell near the isthmus. Vertical view transversely sub- 

 hexagonal-rectangular, with a subconical protuberance 

 in the middle of each side, ends concave, and with the 

 two angles at each end rounded, margins between the 

 central tumour and the polar angles broadly concave ; 

 polar lobe transversely subrectangular, angles subrotund 

 and sides slightly concave. Cell-wall irregularly and 

 somewhat distantly punctate. 



Zygospore unknown. 



Length 58 ^ : breadth 44 JJL ; breadth of polar lobe 

 26 \L ; breadth of isthmus 10 u ; thickness 30 si. 



ENGLAND. In a bog at Lindeth, near Bowness, 

 Westmoreland ! 



This is a very distinctive species, its only near relative being 

 E. Berlini Boldt (in ' Desm. Gronland,' 1888, p. 10, t. i, f. ]2). a 



