Monetaria caputserpentis (Snakehead cowrie)

This species occurs in the Red Sea, Indian Ocean, tropical Indo-West Pacific, Australia and the Philippines. This sea snail lives on corals, rock reefs and rocky shores from the intertidal zone down to depths of 200m. Frequently these shells are sold with a purple top, which is achieved by dipping the dorsum in acid.

In facebook recently there was a discussion regarding specimens from Philippines that are shown alive with a purple top and even specimens being caught in-situ with the purple top and live animals. Apparently there was a factory nearby emitting acidic waste which the animals are absorbing. However, hotly a disputed debate.