I've been following the discussion with amusement and much appreciate the 
true confessions of Paul Monfils and Ferreter.  I got a call several years
ago from a woman whose only shelling experience was at Sanibel.  What she 
called about was a shell she could not identify.  It took no time at all to
realize she had a Lambis species.  She was certain she had found it on the
beach just off the hotel at Sanibel.  I told her no way was it native and 
she was a bit disappointed.