Introduction

Abstract Almost forty years have elapsed since Leonard Wills published his 'Palaeogeographical Atlas of the British Isles'; those forty years have seen a revolution in the earth sciences which has overturned many earlier ideas in geology. Palaeogeography has been affected just as much as other parts of the subject by this change. The advent of the plate tectonic theory has transformed our ideas of the Lower Palaeozoic palaeogeographical evolution of the British area and has rendered totally obsolete many aspects of Wills' maps. The application of plate tectonics has caused us to produce totally new palaeogeographical models for the late Precambrian and early Palaeozoic, and has emphasised that definitive palaeogeographies for this time interval cannot yet be compiled. Wills was at pains to point out that his Atlas was an 'Aunt Sally' at which to 'hurl one's own and other field observations'-our atlas too must be viewed in that light. The Precambrian and Lower Palaeozoic maps are separated for the northern and southern British Isles areas, because for much of that time the two areas were separated by the Iapetus Ocean. The recognition of important terrane boundaries in Scotland and Ireland has led to our attempt to reconstruct a map from the collage of terranes now in juxtaposition. These early maps owe much to Keith Ingham's experience of the Lower Palaeozoic-Keith would insist here that the maps are very much in the 'Aunt Sally' mould, and that his interpretations may not be able to stand the test of time-but they represent