Xll 
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. 
