This field guide describes the highlights of the very abundant and diverse upper Ordovician fauna which lived in a variety of sedimentary environments associated with the several distinct microcontinents and terranes in what are now Great Britain and Ireland. Three introductory chapters cover life in the Late Ordovician, Upper Ordovician stratigraphy and the environmental and tectonic settings of the main successions. A team of 14 experts has described and illustrated many of the key Upper Ordovician fossils, ranging from the abundant brachiopods, trilobites and graptolites to the much less common, enigmatic calcichordates, in ten separate chapters. An extensive bibliography directs readers to the relevant monographs and specialist papers. This pocket sized guide is an essential reference for those interested in the Upper Ordovician of the region, and will also be valuable for students of the European and North American Ordovician.