COSMARIUM. 161 



Xorwav. Sweden. Denmark. Poland. N". Russia. 



fc 



Finland. Greenland. United States. 



This rare species stands near to C. Phaseolus Breb., but is 

 distinguished by its proportionately greater length compared 

 with its breadth, by the straighter and less reniform base of 

 the semicells, and by the broadly tumid (ventricose) sides of 

 the vertical view. Lundell also states that the chloroplasts 

 are like those of C. moniliforme (Turp.) Ralfs, consisting of 

 a number of lobes radiating from a central pyrenoid. 



Forma subrectangularis /. nov. (PL LX, fig. 19.) 



Semicells distinctly subrectangular with rounded 

 angles. 



Length 32' 5 /i ; breadth 2 7' 5 /n ; breadth of isthmus 

 11*2 /i ; thickness 22 /u. 



IRELAND. Ballynahinch, G-alway ! 



This form is characterized by the shape of its semicells as 

 seen in the front view. The punctulations on the cell-wall 

 are larger in the centre of the semicells as in the typical form. 



20. Cosmarium Trafalgaricum "\Vittr. 



(PL LX, fig. 20.) 



Cosmarium Trafalgaricum Wittr. in "Wittr. & Norclst. Alg. Exsic. 1877, 

 no. 81 ; and in fasc. 21, 1889, p. 44 ciirn fig. xylogr. ; Cooke, Brit. Desm. 

 1886, p. 89, t. 43, f . 7 (figure incorrect) ; De Toni, Syll. Alg. 1889, p. 1054. 



Ursinella Trafalgarica Knntze, Revis. gen. plant. 1891, p. 925. 



Cells small, about 1-J- times longer than broad, deeply 

 constricted, sinus linear, widening outwards ; semicells 

 subreniform with a rather flattened base, middle of 

 apex emarginate. Side view of semicell spherical, 

 with a small protuberance on each side. Vertical view 

 elliptic, with a protuberance at the middle on each 

 side, ratio of axes (without protuberances) about 1:2. 

 Cell- wall smooth. 



Zygospore unknown. 



Length 24-26 p.; breadth 20-21 p. ; breadth of isth- 

 mus 6-7 n ; thickness 13-14 /^. 



ENGLAND. In the fountains, Trafalgar Square, 

 London (WittrocJc; 1872). 



VOL. II. 11 



