COSMAIUUM. 273 



species were laid down. We therefore regard Wittrock's 

 " var. Lundellii ' as the type form, and consider that this 

 varietal name came into existence simply because careful 

 observers were beginning to find out that their specimens did 

 not ao'ree with the erroneous figures g-iven by Balis."* We 



*/ 



have examined C. tetraophthalmum from Norway, Germany, 

 Austria, Switzerland, and Italy, and the specimens agree in 

 every detail with those so widely distributed in the British 

 Islands. 



C. tetraophthalmum should be carefully compared with 

 C. cymatopleurum var. tyrolicum. 



Heterocarpvlla tetraophthalma Kiitz. (*' Syn. Diat/ 1834, 

 p. 597; Breb. f Alg. Falaise/ 1835, p. 56, t. 7), Cosmarium 

 tetraophthalmum Menegh. (' Conspectus algol. Eugaiiese/ 

 Patav. 1837, p. 18; ' Synops. Desm.' 1840, p. 220), and 

 Euastrum tetraophthalmum Kiitz. ('Phyc. germ.' 1845, p. 136) 

 are excluded from the synonymy because of the impossibility 

 of deciding to which species of Oosmarium they refer. 



NOTE. We have excluded C. tetraophthalmum var. sub- 

 rotuudum West (' Alg. X. Wales/ 1890, p. 289, t. 6, f. 25) on 

 account of its doubtful nature. The figure is not a good one, 

 and the characters of the Desmid in question indicate rela- 

 tionships quite apart from C. tetraophthalmum. Until further 

 specimens are examined we shall place it among those doubtful 

 forms still to be enquired into. 



* Precisely similar inaccuracies of description and figure led to the estab- 

 lishment of " C. Turpinii var. Lundellii," this having since been shown, by 

 an examination of Brebisson's original specimens, to be typical C. Turpinii 

 (vide p. 191). 



VOL. III. 18 



