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VI institutions as have already been named in previous volumes; also to Mr. C. H. Lankester, of Cachí, Costa Rica, who kindly placed the Tracheophones of his fine collection of Costa Rican birds at the author's service.

To Señor Don José C. Zeledón, of San José, Costa Rica, the author is specially indebted for most generous help, at considerable expense to himself, in making a very fine collection of the birds of that country, which proved of incalculable value in the preparation of this work.

Dr. C. W. Richmond, Assistant Curator, and Mr. J. H. Riley, Aid, of the Division of Birds, U. S. National Museum, have rendered invaluable assistance; Dr. Richmond through his special knowledge of ornithological bibliography and his extremely useful and very complete card catalogue of generic and specific names, made at "first hand," or directly from the publication in which each name was first published, as well as by carefully scanning the proof sheets with particular reference to correctness of citations in the synonymy; Mr. Riley, by copying references from various publications, but especially through having performed the tedious task of measuring several thousands of specimens.

There has been some criticism of the present work on the ground that certain books, local lists, and other publications have not been cited in the synonymies. The omission of these is very much regretted by the author, who in explanation, if not justification, would state that it has been quite impossible for him to cover the whole field; that the literature of ornithology is so vast, and increasing so rapidly, that to bring the bibliography and synonymy of all the species up to date and keep it so would require all the time that any one individual could possibly give to it; and that since much the greater part of this labor (which has justly been termed "the drudgery of ornithology") has been done by the author himself, very largely in his own time (which means during hours which should have been