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ment subinterior, short, inserted in an oblong cardinal cavity in¬ 
creasing with the summit; muscular impression single and sub¬ 
central. 
There is a wide difference of opinion as to the known varieties 
of the oyster family. Defrance enumerates one hundred and 
twenty species, Lamarck thirty-three fossil and forty-nine living. 
A hook might be written.about the historical associations of oys¬ 
ters ; much, too, might be said about the oyster beds and fisheries, 
which give employment to thousands of our industrious popula¬ 
tion ; but all this has so little to do with natural history, that I 
can find no excuse for dwelling upon it here. A curious feature 
in regard to the family of bivalves is the fact that most of their 
shells are broader than long. Take for instance the razor shell 
and then look at the mussel, the why and wherefore of this leaves 
room for endless discussion. 
The anatomical structure of the oyster is more nearly perfect 
than would he supposed, from its apparently low state of organi¬ 
zation. It has a heart, liver and intestinal canal, and a hag near 
the mouth, which answers the purpose of a stomach. Its 
breathing organs are gills, closely resembling those of most other 
fish. It has little vessels which convey the bile from the stomach 
to the liver, and may, perhaps, be subject to bilious attacks as 
well as those who swallow this curious piece of organization at a 
mouthful, without thinking at all of the goodly structure they are 
demolishing. There is the living heart with series of blood ves¬ 
sels, just as perfect as in the larger animals. There are the nerves 
in the shape of minute feelers, which appear to be acutely sensi¬ 
ble, not only of actual contact with foreign bodies, but also of 
sounds and movements from without. A very nice sense of feel¬ 
ing appears to reside in the beard, in scientific language byssus ; 
this is a kind of double fringe to the two lobes of the mouth, or 
sac, as it is called, which envelops the body of the animal, and 
floats free from the shell, except just at the part nearer the valve 
where it is attached. The muscular impressions left on the in¬ 
side of the valves by the adhering muscles of the animal, are 
known in the oyster, mussel, etc., as having but one impression 
and are described as belonging to the class Monomyaria, this 
being known as the abductor muscle. During the life of an oyster 
