An hourly guide that follows twenty-four mollusks to reveal the fascinating lives behind their shells.

From morning to night and from the Arctic to the equator, snails, clams, and other shell-making mollusks have busy days. In this short book, award-winning author and marine biologist Helen Scales shows readers exactly how these animals spend their time. Each chapter of Shell Day features a single mollusk during a single hour, highlighting twenty-four unique species.

We begin our day far in the north, where the Svalbard archipelago lies deep in the darkness of the polar night. And yet, in what remains a scientific mystery, Iceland scallops continue daily rhythms, closing and opening their fan-shaped shells using an internal clock. At noon, we observe a clam shell sitting still on the seabed of a sandy tropical lagoon. The two shells open a crack, and a pair of rounded eyes peep out. A small, rust-colored coconut octopus hiding inside lets the clam shells fall apart and gathers them up in her arms. This mollusk’s ancestors long ago lost the ability to produce their own shells, but she’s happy to use another animal’s cast-off as a temporary home. At ten that night, we find ourselves on a beach in Southern France. A male moon snail uses his huge, fleshy foot like a plow as he digs down into the seabed in search of food. When the moon snail finds a cockle, he swiftly smothers it, then sets about drilling, aided by a daub of acidic slime. Cockles are tasty, but so are other moon snails, and his snacking has a cannibalistic flavor.

For each chapter, illustrator and cartoonist Aaron John Gregory has depicted these scenes with entrancing pen and ink illustrations. Working together to narrate and illustrate these unique moments in time, Scales and Gregory have created an engaging read that is a perfect way to spend an hour or two—and a true gift for beach combers, naturalists, and anyone eager to meet the mollusks that make their favorite shells.