A separately issued edition of the "Introduction" to Gould's Monograph of the Trochilidae, or family of humming-birds, preceded by that work's "Preface" (pages i-iv), and followed by the introduction's "Explanation of the abbreviations" and indexes (with added page references) (pages 183-212). See "Notice" (preliminary pages 7-8): "As the Introduction to my "Monograph of the Trochilidae" involved much intricate and laborious investigation, particularly with regard to the synonymy of the various species, I have been induced to have it set up in octavo for the facility of correction. From this draft, as it were, it has been reprinted in large type for the folio work. Believing that in its present form it might be interesting and useful to many of my scientific friends and others, I have had a limited number of copies printed for distribution among them."