218 BRITISH DESMIDIACE^E. 



1 94. Cosmarium subtrinodulum West & Gr. S, West. 



(PI. XCI, fig. 9.) 



Cosmarium sultrinodulum West & GK S. "West, Notes Alg. II, 1900, p. 292, 

 t. 412, f. 11 ; Nordst. Index Desm. Suppl. 1908, p. 122. 



Cells rather under medium size, a little longer than 

 broad, very deeply constricted, sinus narrowly linear 

 with a dilated extremity ; semicells transversely 

 pyrami date-oblong, basal angles obtuse, apical angles 

 rounded, sides (including superior angles) with 3-4 

 rather distant undulations or nodulations, apex wide 

 and slightly convex ; with 3 small tumours in the 

 centre of the semicells, subtransversely disposed, each 

 tumour surrounded by a ring of small scrobiculations, 

 and also with other minute scattered scrobiculations 

 (or punctulations) round about. Vertical view elliptic, 

 poles undulate, with a slight trinodulose inflation at 

 the middle on each side. Cell-wall thick. 



Zygospore unknown. 



Length 47'5 ju, ; breadth 39 p.; breadth of isthmus 

 11 '5 JLC ; thickness 27 p. 



" ENGLAND. Xear Bowness, Westmoreland! 



This species stands nearest to C. trinodulum Nordst. (' Alg. 

 et Char/ I, 1880, p. 5, t. 1, f. 4), but differs in the disposition 

 of the nodules in the upper part of the margin of the semi- 

 cells^ in the more rounded basal angles, in the general arrange- 

 ment of the central tumours (with their accompanying- scro- 

 biculations), in the inflated vertical view, and the thickened 

 cell- wall. 



195. Cosmarium fastidiosum West & Gr. S. West. 



(PL LXXXV, fig. 11.) 



Cosmarium fastidiosum West & Gr. S. West,, Aig\ S. England, 1897, p. 489, 

 t. 6, f. 11 ; Nordst. Index Desm. Suppl. 1908, p. 59. 



Cells small, a little longer than broad, deeply con- 

 stricted, sinus narrowly linear with a slightly dilated 

 extremity ; semicells trapeziform-semicircular, basal 

 angles rounded, sides convex and 7-8 granulate 



