In “The Sound of the Sea: Seashells and the Fate of the Oceans,” Cynthia Barnett presents us with a glittering Wunderkammer for our age, a staggeringly varied history — scientific, cultural, philosophical and economic — of one of the most beloved and enduring natural objects on Earth: the seashell. To the 16th-century European collector, a Wunderkammer housed a collection of natural and precious objects ranging from the geological, archaeological, ethnological and religious to new works of art. Shells, at one time or another, seem to have represented all of these things, and Barnett’s book buzzes with histories spanning a barely comprehensible 800 million years.