A. CLEVE-EULER, DIAT. FLORA OF FINLAND. 3 



the Arctic Sea, except Caloneis jossilis and Nav. Lihellus. 

 Several of the species may even bo considered characteristic 

 to that sea, viz. Navicula distans, Achnanthes arctica, Synedra 

 kamtschatica, Coscinodiscus curvahdus, Podosira glacialis, and 

 others. It is thus obvious that the strata in question have 

 been deposited by the Arctic Sea at an epoch, when that 

 basin spread over parts of the present Karelen, which epoch 

 probably was that of the old Ancylus-Sea. 



In the introduction of his »Diatoms of Finland», P. T. 

 Cleve enumerates the leading forms of some natural asso- 

 ciations of diatoms, characterising different conditions of 

 climate and water, especially waters of more or less salinity. 

 We there find the association of brackish water, now living 

 along the Baltic coasts of Finland, which proves to have 

 some species, such as Epithemia iurgida var. Westermannii, 

 Melosira Borreri, Coscinodiscus balticus, Campijlodiscus Clypeus 

 and C. Echineis in common with the fossil flora of the Lito- 

 rma-deposits. By the rich development of other species, such 

 as Rhabdoneyna arcuatum and yninutum, GrammatopJiora ocea- 

 nica, Hyalodiscus scoticus, Coscinodiscus asteromjjhalus a. o., 

 the latter, however, bears appearence of having lived in a 

 water of greater salinity, such as is now present in the most 

 southern part of the Baltic. 



To those ecological associations, we can now add one, 

 that may be called the marine-arctic formation. It contains, 

 among many other species of diatoms, the following more 

 abundantly: 



Diploneis splendida Greg. Cocconeis Scutellum Ehb. 



D. Entomon Ehb. C. speciosa Greg. 



D. suhcincta A. S. C. costata Greg, 



D. horealis Grun. C. pinnaia Greg. 



D. major Cl. Achnanthes arctica Cl. 



D. Smithii var.permagnan.YSir. A. septata n. sp. 



Trachyneis aspera Ehb. Campylodiscus angularis Greg. 



Pirmularia quadratarea A. S. C. Thuretii Breb. 



Amphora Proteus Greg. Nitzschia marginulata Grun. 



A. Terroris Ehb. iV. polaris Grun. 



Rhoicosphenia curvata (Kütz.) N. Sigma W. Sm. 



Grun. Synedra af finis Kütz. 



