8 small Cypraea from Mauritius

[dave r]

A subfossil is a term for a very old (thousand years or so) specimen that has not become a proper fossil yet. Subfossils can come from a variety of places, an ancient seabed that has become dry land for some reason; under sand on the seabed, after being exposed by a storm etc. I have an almost identical owenii to yours, and also an esontropia,  that were found when a coral reef was being dug out to extand an airport.
Any shell that is exposed to sunlight will lose it's colour pretty quickly.
Dave.