>> than a land snail on a beach? It's true that storm waves, hermit crabs,
and human collectors can all act against gravity, but

> Andy, a friend of mine went to Hawaii (I don't remember which island) a
few years ago, with strict instructions to bring me a SEAshell.  Well, she
did - said she picked them up on a beach, but they were two fairly large
LANDshells.

> Joan, NASC

Greetings, North Alabama Shell Club! Sounds like you got more than you
reckoned on. I had a similar experience with a native of Taiwan, who
absolutely refused to concede that his beach-collected snails could have
lived on the land. It happens in the Bahamas too, where Stephen Jay Gould's
great love, the rather robust landsnail Cerion, is commonly picked up on
beaches.

The decaying flesh of dead landsnails develops gasses (carbon dioxide,
ammonia, methane) that may be trapped in the shell, making them float.
(Recall that dead bodies tend to float after a few days in the water.) Even
plain old air can make thin-shelled bivalves and landsnails float, and this
can happen with marine bivalves as well as freshwater mussels if their
valves are shut.

Finding seashells on a mountaintop is more unusual, but it does happen, as
Leonardo da Vinci recorded in one of his notebooks. It just takes a few
million years of plate tectonics... a snail's pace indeed.

Andrew K. Rindsberg
Geological Survey of Alabama

----------------------------------------------------------------------
[log in to unmask] - a forum for informal discussions on molluscs
To leave this list, click on the following web link:
http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
Type your email address and name in the appropriate box and
click leave the list.
----------------------------------------------------------------------