For guidance in the course of my study, I am especially indebted to Professor Henry S. Fitch. For suggestions concerning the preparation of the manuscript, I thank Professor E. Raymond Hall. I am grateful to my wife, Janis, for her invaluable assistance and for typing the manuscript.

For use of specimens in their care, I thank Professors William E. Duellman, University of Kansas; Robert L. Packard, formerly of Stephen F. Austin State College; W. Frank Blair, University of Texas; and William B. Davis and

Richard J. Baldauf, Texas Agricultural and Mechanical College. Mr. John E. Werler of the Hermann Park Zoo, Houston, Texas, contributed live individuals; Mr. Richard S. Funk contributed information on the birth of a brood of cottonmouths; and Dr. Henry M. Parrish contributed information on the incidence of snakebite. To numerous other persons at leading museums throughout the United States for information on the cottonmouths in their collections, to all who helped with the field work in various ways, and to others at the University of Kansas for their help and suggestions I am grateful.