Book excerpt: Geerat Vermeij wrote this "celebration of shells" to share his enthusiasm for these supremely elegant creations and what they can teach us about nature. Most other popular books on shells emphasize the identification of species, but Vermeij uses shells as a way to explore major ideas in biology. How are shells built? How do they work? How did they evolve? With these questions in mind, the author lucidly - and charmingly - demonstrates how shells give us insights into the lives of animals in our own day as well as in the distant geological past. As snails, clams, and other molluscs enlarge their shells, they inscribe a detailed record of the everyday events and unusual circumstances that mark their lives. Moreover, the fossil record that chronicles the history of life is replete with shells of extinct species. Vermeij draws on comparisons of shells from different parts of the world and from successive geological periods to argue that predators have played a decisive role in the evolution of shells. Architectural specialization, he argues, is dictated by the risks, rewards, costs, and benefits imposed by predators and competitors on shell-builders living in a dangerous world. This book will be of interest both to amateur shell collectors and to scholars, and its lively review of evolutionary history should prove especially appealing to a general audience.