Nora,
  In the discussion concerning the genera one part of your question was
not answered; is there a book that covers all these changes.  Alas, the
answer is no.  There are some books that will help, but there is no
current up-to-date reference that has all the changes or ever will.  If I
published such a bok, as soon as it came off the press changes in
nomenclature will have occured that would be at odds with what I wrote.
This is the nature of taxonomic and systematic research.
  I try not to get too hung up on the names.  I tend to use a generic name
that helps me put a specimen in my collection where I can find it.  For
families that I have greater knowledge about I may be more up to date on
the currently acceptable manes, for other families I may use only one
genus such as Cypraea.  I do not study this family in great enough detail
that I am up on the subgenera-genera debates and have not labeled these
shells with any genus name other than Cypraea.  Use what works for you.
More important than the correct name is precise locality data.
 Some books to reference are Rosenberg's book mentioned erlier and
Millard's update of K. Vaughn's book on classification.  If the Treatise
of Invertebrate Paleontology ever get the updates on the Mollusca
published, they will be of tremendous assistances.
  Until then, enjoy the shells and don't get too hung up on placing
everything in a neat tiny box.
 
Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History, Pittsburgh, PA
Assistant Professor - Family Medicine
 
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