124 BRITISH DESMIDIACE^l. 



Cells about of medium size, about twice as long as 

 broad, deeply constricted, sinus narrowly linear with 

 a slightly dilated apex ; semicells truncate-pyramidate, 

 lower and upper angles rounded (lower angles very 

 slightly prominent), sides slightly retuse, apex slightly 

 convex. Side view of semicell subelliptic, with two small 

 ridges at and just below the apex, curving outwards 

 and downwards. Vertical view circular, with two 

 small curved ridges (or costae) across the middle from 

 side to side, convex towards each other. Cell-wall 

 very delicately and densely striolate, with four trans- 

 verse series of punctulations, two basal, one median, 

 and one small apical series. Chloroplasts axile, one 

 in each semicell, with a central pyrenoid. 



Zygospore unknown. 



Length 55-60 JJL ; breadth 30 "5 p. ; breadth of 

 isthmus 10/x; thickness 22 p. 



Geocjr. Distribution. Sweden. 



This species should not, perhaps,, be regarded as British, as 

 the only evidence of a British specimen having been found 

 is a very poor drawing in Hassal's ' British Freshwater 

 Algas ; (1845) of a Desmid which that author imagined to be 

 C. quadratum. 



134. Cosmarium Denotarisii (Wittr.) Xordst. 

 (PI. LXXXI, fig. 16.) 



Cosmarium tetraophthalmum De Not. Desm. Ital. 1867, p. 38, t. 3, f. 19. 



[Not C. tetrophthalmum Breb. 1848.] 

 C. tetraophthalmum Breb. var. De Notarisii Wittr. Skandinav. Desm. 



1869, p. 56. 

 C. De Notarisii (Wittr.) Nordst. Desm. Ital. 1876, p. 30; Eoy & Biss. 



Scott. Desm. 1894, p. 100 ; Nordst. Index Desm. 1896, p. 99. 



Cells large, about 1^ times as long as broad, deeply 

 constricted, sinus open and acute-angled, with a 

 rounded apex; semicells elliptic- subsemicircular, dorsal 

 margin much more convex than ventral margin. Side 

 view of semicell broadly obovate-elliptic. Vertical 

 view elliptic. Cell-wall densely and minutely scrobi- 

 culate, scrobiculations largely in concentric series. 

 Chloroplasts . . . . ? 



