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THE OYSTER AND ITS MODE OF LIFE 



Species. — The oyster is classified under the sub-kingdom or phylum 

 of animals called Mollusca — one of about ten such great subdivisions of 

 the Animal Kingdom. Of the four or five classes of mollusks, the one to 

 which the oyster belongs has often been called Bivalvia or Lamellibranchia. 

 In this there are over twenty families, the Ostreidae being one. Its 

 most typical genus, Ostrea, has been said to contain some seventy living 

 and two hundred fossil species. 



Lamarck, in his day, gave brief descriptions of fifty-three living and 

 eighty-two fossil species. He referred eleven living species to America, 

 of which, three are of interest here as occurring on the Atlantic coast of 

 Canada and the United States, namely: 



Ostrea virginica, Gmelin, on the coast of Virginia; 



Ostrea borealis, Lamarck, near New York; 



Ostrea canadensis, Lamarck, at the entrance of the river St. Law- 

 rence and near New York. 



The differences are in the size, shape, and surface of the shell, e.g., 

 whether elongate or oblong-ovate, straight or curved, thick or thin, and 

 in the upper valve being flat or convex, etc. 



Two papers by White and Heilprin enumerate more than one hundred 

 species of fossil Ostreas for this continent alone. 



Those zoologists who have had the advantage of studying living 

 oysters in their natural surroundings and who have extensively collected 

 by hand, by tongs or rakes, and by dredges, on different grounds and from 

 various depths, can easily understand how museum specimens and fossils, 

 dissociated from their companions, may be assorted into many apparently 

 different species. On almost any oyster area it is possible to pick out speci- 

 mens corresponding to Lamarck's three living species before mentioned 

 and to fill in transitional forms. Most of the oysters at Ram Island point, 

 Malpeque, would be classed as 0. borealis; many on the Curtain Island 

 beds would be called 0. canadensis; while numbers of what are locally 

 spoken of as cove-oysters would fall in the type genus 0. virginica. The 

 small Caraquet oyster is perhaps the most constantly divergent variety 

 on our coast, and, as will be shown later, cross-fertilization between it and 

 the very different large Curtain Island oyster can be effected. It is gene- 

 rally understood now, by those who have given attention to the subject, 

 that there is but one living species (Ostrea virginica, Gmelin = 0. virginiana 



