Seashells, stretching from the deep past into the present day, are touchstones leading into fascinating realms of the natural world and cutting-edge science. Members of the phylum Mollusca are among the most ancient animals on the planet. Their shells provide homes for other animals; have been used as a form of money; and have been a source of gems, food, and new medicines.

After surviving multiple mass extinctions millions of years ago, molluscs and their shells still face an onslaught of anthropogenic challenges, including climate change and corrosive oceans. But rather than...