The first three editions of this textbook were published in 1979, 1986 and 1992, and I trust that tins new one, necessitated by so many advances both in fact and theory', will retain its function as a course text for students of palaeontology from their second year onwards. 1 have made substantial changes to Chapters 1-3,7, 8 and 12, and the Trace Fossils section has been transferred from Chapter I to die last chapter. AH the other chapters have been revised to a greater or lesser extent. 1 have redrawn about half of the illustrations: a singularly congenial occupation for long winter evenings, and l hope that these will prove of value in helping students to understand the anatomy and terminology of fossil invertebrates.