164 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



species which are truly or peculiarly IS'orth American and those which 

 are more properly visitants from other countries; but in the case of 

 those whose occurrence appears to be accidental or occasional, the nnm- 

 her preceding the name is inclosed in brackets. Of the latter class, 

 species which there is good reason to believe did not reach our limits 

 through natural means (i e., those escaped from confinement) have been,^ 

 in every case, carefully excluded, as have likewise all introduced species. 



It has been deemed best, in view of the recent discoveries along our 

 southwestern border, to retain as North American all the species (less 

 than a dozen in number) treated by Professor Baird in Volume IX, 

 Pacific Eailroad Reports ("Birds of North America"), and likewise given 

 in the old catalogue, ou account of their having been obtained just across 

 the boundary, in Northern Mexico ; their discovery within our limits being 

 quite certainly only a question of time and investigation. For the same 

 reason, the remaining few of Giraud's "Sixteen New Species of Texan 

 Birds"* are also included. Neither are we prepared to relinquish several 

 Audubonian species which at the present time are known only from 

 the descriptions and figures by their discoverer (e. /y., Regulus cuvieri, 

 Ferissoglossa[^ carbonata, Dendroeca montana, and Wilsonia minuta, as 

 well as other better-known species which are given by Audubon on his 

 own authority {e. g., Chrysomitris ''hnageUanica^' = C. notata, and Eudoci- 

 mus ruber). 



Several species peculiar to the islands of Socorro and Guadalupe, off 

 the coast of northwestern Mexico and Lower California, respectively, 

 together with the few forms peculiar to the latter peninsnla, are re- 

 garded as truly North American, their affinities, with perhaps only two 

 exceptions {i. e., Gonurus holochlorus and Folyborus lutostis), being strictly 

 " Nearctic." 



The greatest difficulty encountered in the compilation of this work 

 has been in the way of distinguishiug between valid "species" aud 

 those forms to be regarded as geographical races of merely subspecific 

 rank. The greatest care has been taken in all doubtful cases of this 

 kind, and previous conclusions (published in "History of North Ameri- 

 can Birds "t and elsewhere) carefully reconsidered, with the aid of all the 

 material accessible, including many specimens not previously in hand. 

 This reconsideration of the subject has, in not a few cases, resulted in a 

 reversal of former opinion, specimens from important localities not be- 

 fore represented often deciding the point one way or the other. Every 

 form whose characteristics bear unuiistakably the impress of climatic or 



* A Description of Sixteen New Species of North American Birds, by Jacob P. 

 Giraud, jr. New York. George F. Nesbitt, printer, Tontine Building, corner of Wall 

 and Vl''ater streets. 1841. Folio, not paged, 8 plates. [For species given in this 

 work, whicb have not since been obtained within the limits of the United States, see 

 p. 229.] 



t A History of North American Birds, by S. F. Baird, T. M. Brewer, and E. Ridgway. 

 Laud Birds. Illustrated by 64 colored plates aud 593 woodcuts. 3 vols., royal 4to. 

 Boston. Little, Brown, & Co. 



