xii PREFACE. 



more numerous than might appear from these reports, the authors have closely confined themselves to 

 such as they actually met with. It is hoped that the work will thus be rendered truly original and reli- 

 able, instead of being merely a compilation of the errors, as well as the facts, of preceding authors. 



Instead of Plates of Birds, Nos. XXI. and XXIV. (which are merely a comparison of the heads, feet, 

 and tails of the common American crow and raven), Plates VII. and VIII. of Birds have been prepared 

 for this Volume, as more generally interesting. (See list of Plates.) 



The liberality of the publishers in authorizing the additions made to the present edition, has enabled 

 the authors to make important corrections, and thus, in some degree, to keep pace with the advance of 

 science. The small number of copies published by Government (1,500) encourages them to believe that 

 this improved edition will be salable in number sufficient to pay the expenses of its publication. 



N.B. — Since printing the preceding pages, it has been ascertained that the Government edition of 

 the volumes containing these reports is not called the eleventh, but " Supplement to Vol. I." 



New York, November, 1859. 



