P. T. Cleve: The Diatoms of Finland. 



i) 



Navicula hebes Ralls. 



y. semen Ehb. 



Achnantlies marginulata Grim. 



Cymbella heteropleura Ehb. 



C. naviculacea Grim. 



Cymbella norvegica Gran. 

 C Cistula var. arctica Lagst. 

 Eunotia Dentlcula Breb. 

 1£. Papilio Ehb. 

 Diatomella Balfouriana Grev. 



Of a less decided arctic character are the following: 



Pinmilaria mesogongyla (Ehb.) CI. 



P. divergentissima Grim. 



P. fofo Breb. 



Neidium bisulcatum Lagst. 



Anomceoneis serians Breb. 



Anomceoneis zellensis Grim. 

 J., exit's Grim. 

 Encyoncma hebridicum Greg. 

 Denticula tenuis var. frigida. 

 Melosira distans Kittz. 



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 w T ater. Purely marine diatoms within the limits of Finland 

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

 only brackish. Characteristic of these brackish waters and oc- 

 curring there in immense number are the following species. 



Mastogloia Smithii Thw. 

 31. elliptica C. Ag. 

 Cocconeis Pediculus Ehb. 

 Achnantlies longipes C. Ag. 

 A. subsessilis Ehb. 

 Rhoicosplienia eurvata (Kiitz.) Grim. 

 Brebissonia Bceckil AV. Sm. 

 Gomphonema olivaceum Ehb. 

 Epithemia turgida var. Westerman- 



nii Kiitz. 

 E. Sorex Kiitz. 



Epithemia gibba (Ehb.) Kiitz. 

 Campylodiscus Clypeus Ehb. 

 C. echineis Ehb. 

 Synedra jmlchella Kiitz. 

 S. affinis Kiitz. 

 Chcetoceras Wighamii Btw. 

 Melosira Borreri Grim. 

 21. Jiirgensii C. Ag. 

 Actinocyclus crassus (W. Sm.) Rail's. 

 Coscinodiscus balticus Grim. 



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 w T ell as in Sweden old Baltic 

 deposits with shells of Mytilus eclulis are found. They generally 

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

 commonly in these deposits are 



