1 86 NEW YORK STATE MUSEUM 



The variability in form noted by Walther as characteristic of a 

 fauna living under brackish -water conditions is shown in the various 

 Champlain localities to some degree by Macoma groenlan- 

 d i c a and Saxicava rugosa; very strikingly by Y o 1 d i a 

 ar c t i c a. 



The Pleistocene fauna of the Hudson valley is briefly considered, 

 but the data are meager. The evidence obtained, however, seems to 

 lead to conclusions similar to those arrived at for the Champlain area. 

 The waters of the Pleistocene Hudson estuary were so freshened 

 going northward that (i) only a few marine forms were able to 

 advance into these waters at all; (2) so far as present knowledge 

 goes only two species reached as far up as Storm King, 50 miles 

 above New York, and none has been reported north of this locality; 

 (3) the two species found at .Storm King represent a dwarf fauna, 

 one of them, Mulinia lateralis, occurring in a dwarfed 

 condition (less so, however) at Croton Point about 20 miles farther 

 south. 



It is recognized that clay deposited in fresh water shows a laminated 

 character not found in similar deposits in very brackish or salt 

 water. The laminated character of the Hudson Valley clays, seen 

 as far south as Haverstraw, and the absence of this peculiar laminated 

 character in any of the localities in the Champlain area where 

 marine fossils were found, verifies what has already been indicated 

 by the distribution and character of the faunas of these areas: 

 (1) that the Pleistocene waters of the Hudson valley were fresh, or 

 practically fresh, north of Storm King; (2) that the Champlain 

 sea extended in a brackish condition to Crown Point and that 

 south of this area its waters were fresh or practically fresh. 



Bibliography 



1 Ami, Henri M. Additional Notes on the Geology and Paleontology of 

 Ottawa and Its Environs. Ottawa Naturalist, 1892, 6:75 



2 Baldwin, S. Prentiss. Pleistocene History of the Champlain Valley. Amer. 

 Geol., 1895, 13:170-84 



3 Coleman, A. P. Marine and Freshwater Beaches of Ontario. Bui. Geol. 

 Soc. Amer., 1901, 12:129-46 



4 Dawson, Sir J. William. The Canadian Ice Age, Montreal, 1894, 

 particularly, p. 58, 209-69 



5 Emmons, Ebenezer. Geology of New York. Surv. 2d Geol. Dist., 1842, 

 p. 128, 283-85 



6 Fairchild, H. L. Postglacial Marine Waters in Vermont. Rep't Vt State 

 Geol. for 1915-16, p. 3-6 



7 . Pleistocene Marine Submergence of the Hudson, Champlain and 



St Lawrence Valleys, N. Y. State Mus. Bui. 209-210, 1919 



