To Professor J. P. Kirtland, Dr. Thomas M. Brewer, Professor S. F. Baird, and Mr. Robert Kennicott, we have also to express our gratitude for very important services, in facilitating the circulation of our work, and for much information and assistance. For facilities for the examination and comparison of specimens we gratefully acknowledge our obligations to the gentlemen of the Academy of Natural Sciences of Philadelphia; to Professor Joseph Henry and Professor S. F. Baird, of the Smithsonian Institution; to the Natural History Society of South Carolina; to Mr. Edward Harris, to the Rev. Dr. Bachman, to Mr. John Krider, to Mr. Geo. N. Lawrence, and to Mr. J. P. Giraud. Of the superior execution of the plates of our work, it is perhaps unnecessary for us to speak, but in justice to Mr. J. T. Bowen, and Mr. W. E. Hitchcock, we may be allowed to say that we regard them as having in this volume fully established a degree of excellence in the production of zoological plates, rarely excelled, if equalled, in this country. Though we hope and fully intend to proceed with a second series of this work, as materials accumulate, especially as the present volume has met with a degree of patronage much greater than we had any right or reason to expect, we have to say to our friends and patrons, that at present we have no definite prospect of such continuation. Should we be favored with life and health, we hope to present two additional volumes or series, each, like the present, complete in itself, for which very nearly a sufficient number of birds are now known as inhabiting the United States, and which are not given by former authors on North American Ornithology. At present, our engagements, we regret to say, render such an undertaking quite impossible. John Cassin. Academy of Natural Sciences of Philadelphia, _November, 1855_. CONTENTS. A Acanthylis, genus Page 249 Accipiter, genus 94 Ammodromus, genus 136 “ ruficeps pl. 20, 135 “ rostratus pl. 38, 226 Antrostomus, genus 235 Aquila, genus 109 Archibuteo, genus 103, 161 “ ferrugineus pl. 26, 159 Astur, genus 93 Athene, genus 188