56 



ARCTIC PROVINCE. 



follow, with some slight revision, are H. P. Miiller 

 for Greenland, and Loven for Finmark. 



About fifty univalves and bivalves are enumerated 

 among Greenland testacea, which do not appear in 

 the European lists ; but this number, since most 

 of them are said to be new, and many are known 

 only by very brief descriptions, will probably, on 

 close investigation, require considerable reduction. 

 On the other hand there are about fifty-four tes- 

 tacea common to Greenland and the Scandinavian 

 seas, and out of this number, thirty range to the 

 Scottish seas. It is a very remarkable fact that the 

 species of shell-fish common to Greenland and 

 Finmark are not all inhabitants of deep or mode- 

 rately deep water, but that among them we find 

 periwinkles (Littorina rudis, var., Groenlandica, and 

 Littorina retusa), the dog-whelk {Purpura lapillus), 

 and the little Shenea planorbis, all of which are 

 inhabitants of the belt between tide-marks ; also the 

 tortoise-shell limpet {Acmcea testudinalis), the com- 

 mon mussel (Mytilus edtdis), and species of Mar- 

 garita and Lacuna, whose dwelling is at the margin 

 of low water, or in the belt of weed immediately 

 succeeding. That these littoral mollusks indicate 

 by their presence on both sides of the Atlantic, 

 some ancient continuity or contiguity of coast-line, 

 is what I firmly believe. The line of migration of 

 most of these shell-fish, was most probably from 

 west to east, from America to Europe, during a 

 different state of physical conditions from those 



