198 BRITISH DESMIDIACE^E. 



Culblean, Aberdeen ; N.W. side of Kerloch, Kincardine 

 (Roy cj- Bissett). Meal Odhar, Perth ! 



IRELAND. Lough Derryclare, Kylemore, and lakes 

 between Clifden and Roundstone, Galway ! Lough 

 Guitane and Sugar Loaf Mt., Kerry ! 



Geogr. Distribution. France. Germany. Austria 

 and Glalicia. Italy. Sweden. Finland. N. Russia. 

 Central China. Japan. New Zealand. Australia. 

 United States. W. Indies. Brazil. 



There is very little distinction between C. nitidulum and 

 C. pseudonitidulum except for the difference in the pyrenoids. 

 The semicells of C. nitidulum are generally more angular with 

 a narrower apex and straighter sides. 



C. nitidulum and C. subtumidum are also very closely 

 related, hnt the semicells of the latter are much more rounded, 

 with broader basal angles, more convex sides, and a less 

 angular apex. 



47. Cosmarium canaliculatum West & G-. S. West. 



(PL LXIV, fig. 4.) 



Cosmarium canaliculatum West & G. S. West, New and Int. Freshw. 

 Alg. 1896, p. 154, t. 4, f. 57 ; Alg. S. England, 1897, p. 485. 



Cells of medium size, about 1-g- times longer than 

 broad, deeply constricted, sinus narrowly linear with a 

 slightly-dilated extremity ; semicells truncate-pyrami- 

 date, basal angles well rounded, sides almost straight 

 or slightly convex, upper angles rounded, apex truncate 

 and slightly convex. Side view of semicell shortly 

 ovate towards the base with a slight swelling on each 

 side. Vertical view elliptic, with a wide protuberance 

 at the middle on each side. Cell-wall very thick, 

 densely and irregularly scrobiculate, causing the 

 exterior to appear slightly rough. 



Zygospore unknown. 



Length 72 ^ ; breadth 51 p ; breadth of isthmus 

 17*5 p, ; thickness 35 //,. 



ENGLAND.- -Near Goring, S.E. Oxfordshire! 



This species is rather smaller than the average examples of 

 Cosmarium pyramidatum Breb., from which it is distinguished 

 by the form of the front view, by its central protuberance, its 



