ANCIENT WATER LEVELS OP CHAMPLAIN-HUDSON VALLEYS 215 



to the locality to be nothing more than conchoidal fracture chips 

 from the checking of the clay as it dried in the sun. Small con- 

 cretions have also been found to constitute the basis of an in- 

 formant's description of fossil shells. If I understand Mr 

 Baldwin's interpretation of the marine limit in the Champlain 

 district he also considered the two localities above mentioned as 

 negligible. 



Ebenezer Emmons^ states that two fossils shells, including 

 Saxicava rugosa, are found the entire length of Lake 

 Champlain, but he cites no locality south of the southermost 

 named in this report nor have I been able to get a record of any 

 such southern extension of the fauna. 



Depth of the suhmergence indicated hy fossils. The bottom of 

 the sea within the reach of continental deposits is a surface slop- 

 ing from the shore out into deep water, and is normally divided 

 into a zone of pebbly and sandy deposits at the shore, a zone 

 of sandy deposits farther out, and still farther out a zone of 

 clay. The pebble and sand zone is the littoral belt; in tidal 

 seas, bared at intervals to the atmosphere. The sand zone 

 proper is in shallow water; the clay zone extends from the 

 sand zone out into deep water. Each zone of bottom varying 

 thus in its lithologic character differs also in its depth of water 

 and consequently the pressure and temperature of the water 

 and thus each zone becomes the abode of different animals. 

 The marine shells found in the clays and sandy clays of the 

 uplifted sea bottom in the St Lawrence and Champlain valleys 

 are, according to Sir William Dawson, like if not identical with 

 those of species noAv living in the lower St Lawrence river and gulf 

 at depths less than 100 fathoms. The beaches of the sea in which 

 the marine shells in the Champlain valley lived should not then 

 ■occur more than BOO feet above the shells. Sir J. W. Dawson 

 regarded the fauna at Beauport, Quebec, as living in from 100 

 to 300 feet of water. The species found there include most of 

 those known in the Champlain valley. Evidences of water 

 levels exist in the Champlain area between 600 and 700 feet 

 above the present sea level. As shown in the diagram [pi. 28] 

 the known localties of marine shells ranging as high from 540 



^Geol. N. Y. 2d Dist. 1842. p.283-8o. . 



