112 BRITISH DESMIDIACE^. 



Length 23 '5-26^ ; breadth, with processes, 32-35 (JL ~ 

 breadth of median part of cell 6 '5-7 ^ ; diam. zygosp., 

 without processes, 20-22*5 [JL ; length of processes about 

 20 fji. 



ENGLAND. Sussex (Rolfs). Halgavor Moor and Ky- 

 nance Valley, Cornwall ! (Rolfs). Kare, but widely 

 distributed in British Isles ! 



Geogr. Distribution. Sweden. United States. Australia. 



This species differs from St. hexacerum (Ehr.) Wittr. ( St. 

 tricorne Ralfs) in the smaller " body ' of the semicells, the 

 cylindrical median part of the cells, with the faintest indication 

 of a constriction, and in the more elongate processes. The latter 

 are also much more elegant, and are dilated towards the extremi- 

 ties. The appendages of the zygospores of St. neglectum are 

 also more complicated than those of St. hexacerum. 



117. Staurastrum dubium West. 

 (PL CXLVI, fig. 4.) 



Staurastrum dubium West, Alg. N. Wales, 1890, p. 19, f. 28 ; Cushman in 

 Bull. Torr. Bot. Club, 1904, p. 583 ; ibid., 1907, p. 614. 



Cells rather over medium size, nearly twice as broad 

 as long, including the processes, deeply constricted ; 

 semicells fusiform, rough with rather flattened granules, 



* CP ^^ 



base of semicell with a ring of granules ; processes 

 inflexed, with tricuspid apices ; vertical view triangular, 

 lateral margins concave, with a row of granules just 

 within the margin ; centre of apex smooth. 



Zygospore unknown. 



Length 40 fi ; breadth 70 pi ; breadth of isthmus 13 p. 



WALES. Capel Curig, Carnarvonshire ! 



Geogr. Distribution.- -United States. 



118. Staurastrum boreale W. & G. S. West. 

 (PL CXLVI, fig. 5.) 



Staurastrum boreale West & G. S. West, Freshw. Alg. Orkneys and Shetlands, 

 1905, p. 27, t. 2, f. 25. 



Cells small, about Ij times broader than long, includ- 

 ing the processes, constriction fairly deep ; semicells 



