184 NEW YORK STATE MUSEUM 



Experiment in the laboratory and observation in the field 

 (information of Dr Raynor Liden and Dr Ernest Anters) have shown 

 that clay deposited in fresh water shows a laminated character that is 

 not found in similar deposits laid down in very brackish or salt water. 

 The Pleistocene clays in the vicinity of Albany and northward show 

 this laminated character very beautifully, and it has been found in 

 the clays of the Hudson valley extending as far south as Haverstraw 

 (Ries, p. 577). This condition of the clays verifies what has already 

 been indicated by the absence of marine fossils : that the Pleistocene 

 waters of the Hudson valley were fresh or practically fresh north of 

 Storm King. In contrast to this, nowhere in the Champlain area 

 where marine fossils were found was this peculiar laminated character 

 noted, which fact, together with the distribution and character of the 

 fossils of this area, indicates that the Champlain sea extended in 

 a brackish condition, gradually freshened, to the vicinity of Crown 

 Point station and that south of this area its waters were practi- 

 cally fresh. 



Summary 



This study of collections made in the Champlain and St Lawrence 

 valleys has led to the conclusion that the character of the Champlain 

 Pleistocene fauna is due in large part at least to decreasing salinity 

 southward in the waters of that time. 



The first part of this paper is given up to a discussion of con- 

 ditions found in the Baltic sea and other freshened bodies of water. 

 The Baltic sea shows a very striking decrease in salinity eastward 

 and in a large way the responses of the fauna to it. As the salinity 

 of the water decreases from that normal for sea water, the fauna 

 changes from one typically marine to one in which only a few marine 

 groups are represented and finally to a fresh- water fauna. Each 

 phylum is affected. The decrease in number of species eastward 

 is very rapid; the Baltic has been described as being faunistically 

 divided into two basins, a western and an eastern, the former marked 

 by a rich fauna, the latter by a strikingly impoverished one. Another 

 striking change in the Baltic fauna is the dwarfing of the euryhaline 

 forms. This has been noted among the worms, crustaceans, fishes, 

 but the best examples are found among the mollusks, notably 

 Mytilus edulis and Cardium edule. In addition to 

 being dwarfed the shells become poor in lime, as exemplified by 

 Mytilus edulis and Macoma balthica (groen- 

 1 a n d i c a) . Examples of dwarfing and decrease in thickness of 

 the shells (in the case of mollusks) due to freshening of sea water 

 have also been noted in the British estuaries, and in the Black and 

 Caspian seas. 



