Okay, Art...here are the auction sites:

1.  Mollusc net (auctions every couple of months -- specimen shells):

http://www.molluscs.net/

2.  George Sangiolouglou's website (auctions every now and then -- specimen
shells):

http://www.geocities.com/Eureka/Plaza/1821/home.html

3.  Hawaiian Shell News (haven't seen an auction in a few months but assume
they will return):

http://www.hits.net/~hsn/

4.  eBay Auction (some specimen shells from dealers like UniverShell Trading
but also many shells from individuals who pass off junk the bought at a
garage sale -- use caution):

http://www.ebay.com/