Illustrations
The colored frontispiece is by Mr. Ernest E. Thompson, whom I have to thank for assistance in preparing the color chart and Key to Families. The scheme of this key, which is founded on natural arrangement and on drawings of anatomical details, is original with him, and that here presented is a slight modification of the one he completed and contributed at a time when he was expected to be a joint author of this work. The numerous pen-and-ink drawings, which add so largely to the value of the work, were made by Mr. Tappan Adney from specimens in the American Museum of Natural History. Some of the full-page half-tone plates are from photographs of groups in the American Museum of Natural History; the larger number, however, were especially designed for this work, with the assistance of Mr. J. Rowley, Jr.