ßO KAARK MÜNSTER STRØM. M.-N. Kl. 



CosiiKiriiiiii Cinilnnu rsiiiii W. Wksi . 

 W. Wkst: Alf^æ Noitli Wales. 



This characteristic species was rare in the plankton of .Sognsvandet. 

 It seems to be essentially a plankton form, which is confined to the western 

 shores of lOurope. 



Size: long. 80 [/, lat. 65 \i., lat. isthm. 27 \).. Small form. 



Cosmariimi drprrssiiiii var. aihoudnim (Boi.in.) W. & G. S. West. 

 W. & G. S. Wkst : Fürth, contrib. Freshw. PI. Scott. Lochs. 



This variety is very characteristic in the Caledonian freshwater plank- 

 ton, but it is not exclusively confined to the plankton. It is however, com- 

 paratively rare in the benthos. 



Cosniariiiiii pacliydcrnmtn var. Æthinpiatm W. & G. S. West. 

 W. & G. S. Wkst : Welw. Afr. Freshw. Algæ. 



The variety seems to be confined to the plankton, and it is one of 

 the very greatest rarities for the algologist, being observed only twice be- 

 fore, viz. in W. Africa and in Loch Shin. It occurred in the plankton of 

 the Figgenelven river. 



Size: long. 69 [i-, lat. 61,5 \j., lat. isthm. 30 \j.. 



Genus Xantliidiuui Fhrbg. 1837. 



Xautliid'uDii aiitilopœimi var. Hebridaruui W\ & G. S. West. 

 W. & G. S. Wkst : Fürth, contrib. thresh w. PI. Scott. Lochs. 



This plankton-variety is generally distributed throughout the whole 

 Country, and is one of the commonest Desmids in the lake-plankton. The 

 variety is distinct, but is connected with the type by a whole range of forms. 



In one instance I have found a specimen with the one half as in the 

 typical form, and the other as in the variety. 



PI. I, Fig. r6. 



Xauthidiuni autilopaitui var. polyinaziiiii Nordst. 



Nordstedt: Norges Desm. 

 This distinct form is rarely met with, but it seems to be principally 

 confined to the plankton. 



Xaiifliidiitii coiifrnvrrsiiiii vcr. plaw toiiicimi W. & G. S. West. 

 W. &L G. S. West: Scott. Freshw. l^lankton. 



I have observed this interesting species from a single lake only, where 

 it occurred in small quantities. It is a characteristic plankton variet}', and 

 is widely distributed in the Caledonian plankton area. 



Genus Art/irodrs/iins Ehrbg. 1838. 



Artlirodcsiiiits Iiinis var. Hiiiffrldtii var. nov. 



Cells rather small, slii^litlv broader than loiii:; iKÙthaiit the spines), deeply 

 constneted, sittus open, outer parts angled, seiiiieells subtrapeziponn, apex 



