226 BRITISH DESMIDIACE.E. 



deep concavity in the middle. Cells attached together 

 by the projecting parts of the apices to form fragile 

 filaments, which readily break. Filaments destitute of 

 a mucous sheath ; cell- wall smooth. 



Zygospore globose, provided with simple straight 

 spines ; rarely irregularly angular, with the angles 

 produced. 



Length 8*5-12 ^ ; breadth 7*5-10 JJL ; thickness 5-6 JJL ; 

 breadth of isthmus 3'5-6fx; diam. zygosp. without 

 spines 9-1 a ; with spines, 1 5-1 6 \L . 



ENGLAND.- -Bog 2 m. S. of Clapham, W. Yorks ! 

 Enbridge Lake, Hants (Roy). 



IRELAND. Near (Plenties, Donegal ! Kylemore, Gal- 

 way (Arch.). Slieve Donard, Down ! Shores of Lough 

 Neagii. 



SCOTLAND. Slewdrum, Loch Dawan, and Mosston 

 Moor in Cromar, Aberdeen (Roy & Biss.}. 



Geogr. Distribution. C4ermany. C4alicia and Austria. 

 Spain. Scandinavia. Poland. Australia. 



7. Spondylosium tetragonum West. 

 (PI. CLXI, figs. 12-14.) 



Sphcerozosma (Spondylosium) pulchdlum Gay, Monogr. loc. Conj. 1884, 



p. 79, t. 3, f. 1. 



? Sph. bambusinoides Heimerl, Desm. alpin. p. 589, t. 5, f. 1 (form). 

 Spondylosium tetragonum West, Alg. W. Ireland, 1892, p. 115, t. 19, f. 2 ; 



West & G. S. West, Rec. publ. Desm. 1895, p. 65 ; Freshw. Alg. Columbia, 



1912, p. 1046, t. 23, f. 55-57. 

 Sp. Treubii Bernard. Alg. unicell. domaine Malais, 1909, p. 21, t. 1, f. 16. 



Cells minute, slightly longer than broad, slightly and 

 broadly excavated at the isthmus, sides rounded, apex 

 of semicells truncate ; in vertical view elliptical ; in 

 side view oblong, very slightly constricted. Cells united 

 into twisted colonies, destitute of a mucous sheath. 



Zygospore unknown. 



Length 8'5-lOfji ; breadth 10 pi; thickness 6^; 

 breadth of isthmus 8 [i . 



IRELAND.- -Kylemore, Galway ! 



Geogr. Distribution.- -France. Switzerland. Finland. 

 Java. Colombia. 



