Volume IV starts with a foreword of Gisela P. Padilla-Concepcion. She is Professor at the University of the Philippines, Diliman where she occupies the Chair of the Marine Science Institute. Gisela is one of the main motors behind the Marine Sciences in the Philippines and Diliman is a gigantic University in Manila. This is followed by a foreword of Dr. Yves Finet from the Natural History Museum of the City of Geneva, Switzerland. Yves is a long-time friend of the author and is for many years already in charge of the Lamarckian collection, among his many other tasks. This volume documents 1005 different species, with thousands of images, on 301 plates and counts 680 pages. Collaborating experts in this volume are: Bruno Anseeuw, Gene Coan, Roland De Prins, Henk H. Dijkstra, Takuma Haga, Annie Langleit, Jorgen Lützen, Takashi Okutani, Bernd Sahlmann, Sheila P. Tagaro, Jan Johan Ter Poorten, Rudo von Cosel and Richard C. Willan. The rest of the families has been done by Guido T. Poppe. This book continues first with the Bivalvia, starting with the popular Propemussiidae and Spondylidae. A long list of smaller families follows, but there is extensive coverage of the amazing Septibranchia, especially of the striking Cuspidariidae. Lucinidae are well covered, including the very deep water ones, as they have been studied by the MNHN. Many species are illustrated for the first time in color. Follows another favorite among collectors: the Chamidae with no less than 18 species. Cardiidae get a full coverage by Jan Johan ter Poorten: a surprising 81 species. Tellinidae, Psammobiidae and Mactridae are other big families in the Philippines. After the Bivalvia we continue with the Scaphopods. Amazingly this small area on the global map has an impressive 78 determinated species. The Cephalopods have been documented as well and there is a superb set of photographs of living animals. This volume has two Addenda: Addendum I - As discoveries by Conchology, Inc. and scientists worldwide go on, there is a constant influx of new knowledge. We figure in Addendum I not less than 287 species not documented in Volume I & II because either not yet described or not yet discovered at the time of writing, or rediscovered in the Archipelago. Addendum II - This is an indispensable tool for conchologists working on the mollusks from the Philippines. It gives in 7 pages a summary of the complete literature that concerns this region of the world. This volume completes the main body of the Philippine Marine Mollusks I to IV which now counts not less than 1315 full page A4 color plates.