The student who wishes to consider all the forms in a given region will find it necessary to refer to the Index. Because of my method of treatment, I was compelled to ignore geographical lines. Otherwise endless repetition would result. The only exception to be noted was made in favor of Professor Montgomery’s paper. I am especially indebted for assistance in the preparation of this work to my colleague, Charles Peabody, Ph.D., Honorary Director of the Department of American Archæology, Phillips Academy, Andover, Mass., and also connected with the Peabody Museum of Harvard University. Having access to the great library of Harvard University, he kindly took in charge the Bibliography covering necessary titles for the information of readers and students. While the result does not embody every reference, yet it is the most extensive list ever presented up to the present time. Messrs. Montgomery, Barr, and Brown also added a number of titles. Dr. Peabody’s interest in “The Stone Age” and his unselfish labors and his many suggestions and advice were potent factors in making the work possible. I am also under particular obligations to about forty-five persons who have been kind enough to assist in the making of illustrations for “The Stone Age.” It is no more than fair to state that without this coöperation it would have been impossible for us to present so many figures and such excellent photogravure plates, and at the same time offer the two volumes at the price named in the original circulars. Colonel Bennett H. Young, of Louisville, Kentucky, has made for me about fifty half-tones of type-specimens in bone, shell, clay, and stone which he used in his work “Prehistoric Men of Kentucky,” and also in “Discoveries in Kentucky Caves,” just published. Mr. F. P. Graves, of Doe Run, Missouri, a friend of mine for more than twenty years, made eight photogravure plates of the best specimens in his collection and presented these for use in “The Stone Age.” Mr. B. W. Arnold, of Albany, New York, sent me by express a portion of his collection, comprising some of the most beautiful projectile points and knives of semi-precious stone that it has ever been my privilege to examine. In order to emphasize the high workmanship and beauty of these points, Mr. Arnold had five colored plates made. Color reproductions and photogravures do justice to the art of stone-age man. I am particularly indebted to both Messrs. Graves and Arnold for their kindness in making possible these fine plates. Professor William C. Mills, Curator of the Ohio State Archæological Society and State University Museum at Columbus, and Mr. Clarence B. Moore of Philadelphia, loaned me plates illustrating specimens found during their explorations.