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them. Dead shell are much easier to
store as they can be kept in a box or
bag.
If you do collect some freshwater
musselshells, it is important that you
record where and when you found
them. To a museum, a specimen
without collection information is of
little or no interest.
Identification of Freshwater Mussels
Hands down, the best way to learn
how to identify freshwater mussels is
to accompany someone who knows
them. Having the shell in hand while
someone points out how to identify
them is invaluable. The next best way
is to take your collection to an expert
and have them help you out.
This guide does not include an
identification key. Freshwater mussel
keys are notoriously error-prone.
Species' shells can vary in size, shape,
color and thickness which often lead
one astray when using a key. Instead,
you can compare your shell to the
illustrations and the descriptions to
make a best guess as to what you
have. I also recommend that you
obtain books and guides from other
states. I have several and use all of
them when working with a difficult
shell or something that I haven't seen
before. Also, these will also have
species that are not found in this
guide so that, if you have something
new, these may help you identify it.
There is some terminology that may
be useful when reading the
descriptions or using a key. Most of
these are covered in the Anatomy
section but here are two others.
"Inflated" and "Compressed". These
refer to how "fat" the shell is. A
"compressed" shell is fairly flat
keeping in mind that there still has to
be room inside for the mussel's
internal organs. An "inflated" shell is
fatter than a "compressed" shell.
Imagine putting a straw into the shell
and pumping air in like a balloon,
causing the shell to "inflate". This is
"inflated".
Plasticity
A complication in identification is that
the shape of freshwater mussels can
vary with their environment. The
changes in shell shape are not willy-
nilly but tend to follow a definite
pattern that can be observed when
moving from small headwater streams
downstream into large rivers. This
observation led Dr. Arnold Ortmann to
develop what is now known as
AOrtmann=s Law@.
3, 38
He said:
