Hello Corynne,

Nice quality shells can be obtained on Ebay, but there is a much greater
range of quality than you would find in purchasing shells from a reliable
shell dealer.  Of course, some of the sellers on Ebay are reliable shell
dealers, but others are people who obviously know little about shells.  I
frequently see shells on Ebay that are misidentified, sometimes a common
shell listed as a similar rare species. There are rare shells offered on
Ebay that are poor specimens that have been repaired and painted.  I have
seen shells described as "exceptional quality", where in the picture
provided I can see scars or broken spines or a hole in the shell.  Also,
many collectors (all serious collectors really) place a high value on the
collection data that accompanies the shell.  Some shells on Ebay are offered
with data, but many are not.  So you do have to be careful.

I looked up the two shells you mentioned.  There are 4 Tonna sulcosa listed,
ranging from small to average size, and from fair to fine quality.  The
last-listed one looks best.  It's a common shell, and I wouldn't pay more
than $5.00 for it.  The Murex appears to be quite nice in the dorsal view.
The ventral view is not provided. It's average size and appears to be in
nice condition for this size (this species often accumulates a lot of
erosion and boring damage as it gets larger).  There are a few fine borings
on the dorsal side, but this is minor and practically unavoidable in this
species. There probably isn't an operculum, which is important to many murex
collectors.  I would bid up to about $12.00 if I wanted this shell.

There are many good books available.  The Compendium of Seashells is a
favorite with general collectors for identifying shells, as it pictures
several thousand species from all the common families.  General books like
this are the best to start with.  Later you may wish to purchase books which
are more comprehensive either for a specific family of shells or for a
specific geographic area.  If you do a Google search for this book title,
you will find a number of shell book dealers who list this volume, and see
what other titles they offer as well.

For determining fair values of shells, go to http://www.ofseaandshore.com
Click on "Publications".  There you will find "A Catalog of Dealers' Prices
for Shells", which is an essential reference for anyone purchasing or
selling shells.  A new issue of this work is due out this month.  I don't
know if it is ready yet.

There are also many good websites that will give you a lot of help.  Try
these for starters:

http://www.seashell-collector.com
http://www.conchologistsofamerica.org
http://www.manandmollusc.net

These sites provide a wealth of basic information, and also links to many
other sites.

Regards,
Paul Monfils

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