For a long time between collecting and cleaning at home, put the shells
in isopropol (rubbing) alcohol in a small container.  Film containers
for small shells (readily available as you take pictures or from
anyplace that develops them), oleomargarine containers for larger ones.
 Put containers in a zip lock bag, and that bag in another ziplock bag
to prevent leaks and lessen odor.  Usually, I triple the ziplock bags,
putting several smaller bags in larger ones.

For a short period between collecting and cleaning at home, just jamb
toilet paper in the aperture and wrap in more toilet paper (available
most everywhere).  Then put in double or triple zip lock bags.  The
animal will start to rot and be easy to remove and still have opercula.
Any available deodorant would be desirable.

Be sure to put labels on the containers so you will remember the data
for each collecting station.
--
                     Aloha from Wesley M. Thorsson
Editor of Internet Hawaiian Shell News, a monthly Internet Publication
           122 Waialeale St, Honolulu, HI  96825-2020,  U.S.A
       http://www.hits.net/~hsn                 [log in to unmask]