Hi Charlie & all,
On Key Biscayne, Florida, I found 3 Indo Pacific shells: Turbo chrysostomus,
Strombus aurisdianae and Strombus urceus - these were algae stained and had a
living hermit crab inside - I kind of think these were either from places that
sell live hermit crabs in shells and then they got tossed into the ocean, or
that someone dumped shells from a "tourist basket" into the water and nature
took over.  Also I remember a story from years ago that someone found a Mitra
mitra at Sanibel Island that was 'kind of ripe' from whatever had been living
inside it.  Who knows!!??
Carol in Miami