Book excerpt: From the tiny shrew to the black bear, Pennsylvania's hills and valleys are teeming with sixty-three species of wild mammals. Many of these animals are rarely seen except when pursued by an interested biologist, mammologist, or nature photographer. Now, with the publication of this book, student, scholar, and nature lover alike will have a ready reference to distinguish between a deer mouse and a white-footed mouse, to identify raccoon tracks, and to learn about Pennsylvania's other inhabitants. An attractive backpack-size volume, written in lively prose, the Guide to the Mammals of Pennsylvania opens with a short introduction to Pennsylvania's environment and the characteristics defining a mammal. The bulk of the book consists of species accounts of the mammals grouped into families and orders. Each account includes a short list of data, a Pennsylvania range map, a North American range map, and a narrative of the physical, ecological, and behavioral characteristics of the species. Exciting photographs of each of the species in its natural habitat, 17 in color, and drawings of animal tracks are especially useful for identification, and a glossary and a bibliography provide definitions and references for the serious reader. Naturalists, whether amateur or professional, will find the book useful in the field; it will be an indispensable tool in the classroom.