FRESHWATER ALGÆ FROM TUDDAL IN TELEMARK. 171 



127. Cosmarium tenue. Arch. 

 Rare, only in one or two samples. 



128. Cosmarium tinctum. Ralfs. 

 Scarce. 



129. Cosmarium contractum. Kirchn. 



Rare. The typical C. contractum is rare in the benthos, 

 but one of the commoner desmids in the Norwegian freshwater 

 plankton. 



129 a. var. ellipsioideum. (Elfv.) W. & G. S. West. 



forma 2. W. & G. S. We.st: Brit. Desmid. vol. II, p. 173, 

 pi. LXI. fig. 33. Printz : Ghloroph. Norwegen, p. 20, tab. II, 

 fig. 23-25. 



This form, described by West and Printz was one of the 

 commoner desmids at Tuddal, and often occurred in abundance. 



forma 1. in West: Brit. Desmid. PI. IV, fig. 3. 



130. Gosmariuin depressum. (Nag.) Lund. 

 Somewhat rare, only in a few samples. 



131. Cosmarium Hammeri. Reinsch. 

 Scarce. 



132. Cosmarium granatum. Breb. 

 General, but scarce. 



133. Cosmarium suhtumidum,. Nordst. (Incl. var. Klebsii.) 

 This species was very frequent at Tuddal. Indeed, I think 



it was the desmid, which was the most generally distributed. 

 Size: long. 31 u, lat. 27,6 /li, lat. isthm. 9,5 in. 



134. Cosmarium pseudonitidulum. Nordst. 

 Scarce. 



135. Cosmarium nitidulum. De Nolaris. 

 Very rare. 



136. Cosmarium Tuddalense sp. nov. 



Cells very large, about 1,4 times as long as broad, deeply 

 constricted, sinus narrow, semicells subsemicircular-ovate from a 

 broad base, basal angles well rounded, lateral margins convex, 



