P. T. Cleve: The Diatoms of Finland. 



Navicula hebes Raits. 



N. semen Ehb. 



Achnanthes marginulata Grim. 



Cymbella heteropleura Ehb. 



C. naviculacea Grim. 



Cymbella norvegica Gran. 

 C. Cistula var. arctica Lagst. 

 Eunotia Denticula Breb. 

 £". Papilio Ehb. 

 Diatomella Balfouriana Grev. 



Of a less decided arctic character are the following: 



Pinnularia mesogongyla (Ehb.) CI. Anomceoneis zellensis Gran. 



P. divergentissima Gran. J., ejci^'s Gran. 



P. fafa Breb. Encyonema hebridicum Greg. 



Neidium bisidcatam Lagst. Denticula tenuis var. frigida. 



Anomceoneis serians Breb. Melosira distans Kiitz. 



The quantity of salt in the water exercises an immense in- 

 fluence on the diatoms, very few species being common to fresh 

 water aud brackish water, and scarely any to fresh water and 

 salt water. Purely marine diatoms within the limits of Finland 

 are not found, the water of the Baltic and its tributuaries being 

 only brackish. Characteristic of these brackish waters and oc- 

 curring there in immense number are the following species. 



Mastogloia Smithii Thw. 

 M. elliptica C. Ag. 

 Cocconeis Pediculus Ehb. 

 Achnanthes longipes C. Ag. 

 A. subsessilis Ehb. 

 Rhoicosphenia curvata (Kiitz.) Gran. 

 Brebissonia Boeckii W. Sm. 

 Gomphonema olivaceum Ehb. 

 Epithemia turgida var. Westerman- 



nii Kiitz. 

 E. Sorex Kiitz. 



Epithemia gibba (Ehb.) Kiitz. 

 Campylodiscus Clypeus Ehb. 

 C. echineis Ehb. 

 Synedra pulchella Kiitz. 

 S. affinis Kiitz. 

 Chcetoceras Wighamii Btw. 

 Melosira Borreri Gran. 

 J/. Jiirgensii C. Ag. 

 Actinocyclus crassus (W. Sm.) Raits. 

 Coscinodiscus balticus Gran. 



In the northern part of the Bay of Bothnia the water be- 

 comes more and more fresh and some of the above named spe- 

 cies cease to live there, as Brebissonia Bceckii, Campylodiscus 

 Clypeus and C. echineis. 



In many parts of Finland as well as in Sweden old Halt it- 

 deposits with shells of Mytilus edulis are found. They generally 

 contain diatoms, more or less abundant. The species found most 

 commonly in these deposits are 



