The aim of the Treatise on Invertebrate Paleontology, as originally conceived and consistendy pursued, is to present the most comprehensive and authoritative, yet compact statement of knowledge concerning invertebrate fossil groups that can be formulated by collaboration oLcompetent special- „ ists in seeking to organize what has been learned of this subject up to the mid-point of the present century.

Cretaceous ammonites belong to the four suborders Phylloceratina, Lytoceratina, Ammonitina, and Ancyloceratina. The longranging Phylloceratina extend from low in the Triassic to the top of the Cretaceous, and those that occur in the Cretaceous belong to genera that originated in the Jurassic or are closely related to them.

The late Dr. T. Wayland Vaughan, who had long been interested in marine ecology and paleoecology, in 1940 planned and organized a Subcommittee on the Ecology of Marine Organisms as a part of the Committee on Geologic Research (Norman L. Bowen, Chairman) in the Division of Geology and Geography of the National Research Council of the National Academy of Sciences. The members of this Subcommittee were: C. H. Edmondson, Remington Kellogg, Harry S. Ladd (Chairman), Kenneth E. Lohman, Roger Revelle, F. W. Rolshausen, H. C. Stetson, T. Wayland Vaughan.

This book is a collection of papers on an aspect of plate tectonics of which our understanding is at present limited. In the mid-1970s, prior to the recent phase of IPOD active margin drilling, few geologists would have anticipated that at the start of the 1980s so many new questions concerning the nature of tectonic and sedimentary processes in forearc regions would have come to light.