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Recent and Pleistocene Marine Shells of James Bay

Horace G. Richards
The American Midland Naturalist
Vol. 17, No. 2 (Mar., 1936), pp. 528-545
DOI: 10.2307/2419977
Stable URL: http://www.jstor.org/stable/2419977
Page Count: 18
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Abstract

Only five species were noted from the present marine molluscan fauna of James Bay. Of these, three are more or less characteristic of brackish water [Paludestrina minuta (Totten),Littorina rudis (Maton) and Macoma balthica (Linne)]. The other two [Mytilus edulis Linne and Acmaea testudinalis (Muller)] are more truly marine; however, further collecting, particularly in deeper water, will undoubtedly yield more species. Pleistocene marine deposits have been noted along the Moose River and tributaries as well as along other rivers that flow into James Bay. These are thought to be of post-glacial age deposited as the Wisconsin glacier withdrew to the north and when the land was iow because of the weight of the ice. The release of the load of the ice caused the land to rise and the sea to withdraw to the north. A layer of silt containing freshwater and land mollusks is evidence for this stage. Many shells found on the beaches of James Bay, particularly on Charlton and Cary Islands, are very worn, and have not been found living in the Bay. It is thought that these are Pleistocene fossils deposited when James Bay was deeper and more saline than at present; many of these species are at present living in Hudson Bay proper. There is certainly evidence of a marine interglacial stage or at least that the Wisconsin ice rode over an earlier marine deposit and redeposited shells with the till; it does not necessarily follow that the interglacial sea extended beyond the present limits of James Bay. Other evidence of an interglacial sea may have been obliterated by the Wisconsin ice.

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