106 New York State Museum 



Examples of dwarfing due to freshening of sea water 

 have been noted elsewhere than in the Baltic. The Euro- 

 pean Cockle is very common along the British coast, but 

 it is found in a dwarfed condition in the brackish waters 

 of the estuaries. The shell is also thin and with less 

 strongly marked surface characters. The cockle of the 

 Greenland estuaries has a shell that likewise is thin, 

 smooth and almost without teeth. Both the Caspian and 

 Black seas have fresher water than the Atlantic, and they, 

 too, show dwarfing of the cockles. Among other species 

 that are dwarfed by brackish waters, are the Long or 

 Soft Shell Clam {My a arenaria) and the Periwinkle 

 {Littorina littorea). Even higher forms are affected. 

 Dwarfed fishes have been found in the Baltic and the 

 Black seas and the modifying effect of brackish water 

 on the fishes has been noted elsewhere. 



A recent study by the writer of the Pleistocene fauna 

 of the St Lawrence-Champlain area brought out the fact 

 that the Champlain fauna is a dwarf fauna, due in large 

 part at least, to decreasing salinity southward in the 

 waters of that time. The conditions were similar to 

 those in the Baltic today. The dwarfed character is par- 

 ticularly well-shown by five species : Macoma balthica 

 (groenlandica), Saxicava rugosa, Yoldia arctica, the 

 Common Mussel {Mytilus edulis) and the Long Clam 

 (Mya arenaria). Just as is found in the Baltic, so here, 

 along with the dwarfing of species goes a decreasing 

 thickness of shell and there is some variability of form. 



Bearing in mind all these facts, we can understand bet- 

 ter the effects of changes in salinity of the water at the 

 shore. Rivers and streams are constantly bringing fresh 

 water from the adjacent land to the sea and it is the lit- 

 toral waters that are affected. The effect of these fresh 



