Since the inception of the Atlas of Mammalian Chromosomes, it is a surprise to us that we have finished five volumes with karyotypes of nearly 250 mam­ malian species. We acknowledge the fact that there are many imperfections in this series, but we also hope that these volumes have been useful to various investigators. Springer-Verlag has made a binder which will accommodate the material of all five volumes. We also revised our index to facilitate easy reference. If the material is arranged in the binder according to the Cumulative Contents, we believe one will find it convenient to consult with this book. Volume 5, as in the previous volumes, contains a Cumulative Index, Cumu­ lative Table of Contents, as well as an individual Index and Table of Contents for Volume 5. Previous Indices and Tables of Contents should be discarded. October, 1970 T. C. Hsu Kurt Benirschke v Instructions A special vinyl binder is available from the publisher which will accommo. date the material of the first five volumes. Twenty dividers have been provided with printed tabs. These dividers are intended to separate the Orders and the Index. It is suggested that the dividers be placed in the following sequence of Orders, which sequence will be followed in the future when presenting karyo.