Ivan,
 
Welcome to Conch-L.  After 25 years of USAF life, its nice to have you
guys holding down the fort so I can enjoy the pension.  Hope you enjoy
shells as much as I now do.  I only regret that I wasn't able to do some
serious collecting while I was in the military.  As for the land
shells.  That island is renown for having some really nice land shells.
A word of caution, they are not the same as a sea shell and should not
be cleaned in a strong Clorox solution.  The whole animal can be frozen
and then briefly heated in a microwave.  Some people skip the microwave
part as it could cause the shell to crack.  In that case just let the
shell thaw, pull it out with tweezers and rinse any remains out with a
strong jet of water.  This should enable you to remove most of the
animal.  A little hydrogen peroxide will usually oxidize what ever is
left and the shell can be gently cleaned with soap and water and then
sprayed with a little silicon lubricant to bring out the colors.  Some
where in the Conch-L archives there are a couple of decent
instruction/guides for cleaning shells.  Also, the site recommended
previously for books has a book on cleaning shells.  Good luck, both
with shelling and the Corps.
 
Tom Eichhorst in New Mexico, USA