38 BRITISH DESMIDIACE^E. 



Var. bicrenatum Norclst. (PL XCVIII, fig. 15.) 



C. crenatum var. bicrenatum Nordst. Desm. Spetsb. 1872, p. 30, t. 6, f . 10 ; 



Desm. Ital. 1876, p. 35 ; Boldt, Desmid. Gronland, 1888, p. 18 ; Roy & 



Biss. Scott. Desm. 1894, p. 44. 

 C. bicrenatum Joshua, Notes Brit. Desm. II, 1883, p. 291 ; Cooke, Brit. 



Desm. 1886, p. 96, t. 42, f. 13. 



Semicells with only two lateral cremations. 



Length 24-33 p, ; breadth 17'5-26/*; breadth of 

 isthmus 9'5-11/x,; thickness 12 15/x. 



ENGLAND.- -Leicestershire (Roy). 



SCOTLAND. Not uncommon, but scarce (Roy fy 

 Bissett). 



Geof/r. Distribution. Italy. Norway. NovaZembla. 

 Spitzbergen. Greenland. Siberia. 



243. Cosmarium Grantii Roy & Biss. 

 (PI. XCI, fig. 11.) 



Cosmarium Grantii Eoy & Bis?. Scott. Desm. 1894, p. 102, t. 1, f. 10; 

 Nordst. Index Desm. 1896, p. 134. 



Cells small, almost as long as broad, deeply con- 

 stricted, sinus linear ; semicells subsemicircular- 

 rectangular, basal angles scarcely rounded, margin 12- 

 crenate, four up each side and four at each apex, the 

 three lower lateral crenations rather smaller than the 



others, with a radiating series of about six very minute 







bmate granules within each crenation, and in the middle 



immediately above the isthmus with two horizontal 

 series of conspicuous granules, five in each series. 

 Side view of sernicell subquadrate, basal and apical 

 angles rounded, sides slightly retuse in the upper 

 portion, apex truncato-convex, with two granules on 

 each side just above the isthmus. Vertical view 

 elliptic-oblong, with a broad inflation at the middle 

 on each side. 



Zygospore unknown. 



Length 34-35/i; breadth 30-31 p. ; breadth of 

 isthmus 13-14 p.; thickness 15-lG/i. 



SCOTLAND. Grlassel and Slewdrum, Aberdeen ; 

 Letterbeg in Strachan, Kincardine (Uoy $ Bissett). 



