FRESHWATER ALGÆ FROM TUDDAL IN TELEMARK. 189 



Genus Tetraëdron. Kützing 1845. 



286. Tetraëdron caudatum. (Corda) Hansgirg. 

 Rare. 



287. Tetraëdron hastatum. (Rabh.) Hansg. 

 var. palatinum. Schmidle. 



Rare, in a single sample. 



Genus Ankistr odesmus. Corda em. Ralfs 1848. 



288. Ankistr odesmus falcatus. (Corda) Ralfs. 

 In a single sample. 



Genus Elakatothrix. Wille 1898. 



289. Elakatothrix gelatinosa. Wille. 

 In the plankton. 



Genus Kirchneriella. Schmidle 1893. 



290. Kirchneriella lunaris. (Kirchn.) Moebius. 

 General, but somewhat scarce. 



290 a. var. Dianœ. Bohlin. 

 Very rare. 



Genus Crucigenia. Morren 1830. 



291. Crucigenia rectangularis. (Näg.) Gay. 

 Somewhat rare in the plankton. 



Genus Scenedesmus. Meyen 1829. 



292. Scenedesmus hijugatus. (Turp.) Kiitz. 

 Quite common. 



293. Scenedesmus Hystrix. Lagerh. 

 Scarce. 



