PREFACE. 
A PREFACE is indispensable in this instance, simply because I have no other 
opportunity of properly acknowledging the assistance I have received in preparing 
this work. I am particularly indebted to Mr. J. A. Atten, of Cambridge, Mass., 
who has diligently revised nearly all the proofsheets, and whose critical suggestions 
have proved invaluable. Mr. Roperr Ripeway, of Illinois, has given me the 
benefit of his still unpublished studies of the Raptores and some other groups, 
besides rendering, as Mr. ALLEN also has, various essential services. 
Prof. Barrp kindly offered me the use of all the illustrations of his late 
Review, while Prof. Acasstz generously placed at my disposal the plates 
accompanying Mr. Arien’s Memoir on the Birds of Florida. Several of the 
woodcuts have been taken from Prof. Tenney’s Manual of Zoology, with the 
author’s permission; and a few others have been contributed by Messrs. Len 
and SHEeparp. With a few exceptions, the rest of the illustrations have been 
drawn from nature by the author, and engraved by Mr. C. A. Waker. 
I have spoken elsewhere of Prof. Marsu’s almost indispensable codperation 
in one part of the work. 
While material for the greater part of the descriptions has been furnished by 
the author’s private cabinet, the Synopsis could hardly have been prepared without 
that free access to the collection of the Smithsonian Institution, of which I 
haye been permitted to avail myself. 
The only word of explanation that seems to be required is with regard to the 
large number of genera I have admitted. I have been led into this—unnecessarily, 
perhaps, and certainly against my judgment—partly by my desire to disturb a 
current nomenclature as little as possible, and partly because it is still uncertain 
what value should be attached to a generic name. Among wading and swimming 
birds —the groups of which are, on the whole, more precisely limited than those of 
Insessores—I have, however, indicated what I consider to be a reasonable reduc- 
tion; and on another occasion I should probably extend a like practice, if not one 
even more ‘‘conseryative,’ to the remaining groups. I will only add, that I 
consider that several of the admitted families of Oscines will require to be merged 
‘im one. These are the Twrdidew, Sazxicolide and Sylviide, if not also the Troglo- 
dytidee and Motacillide ; while the same may prove true of the current Sylvicoline, 
Tanagrine and Fringilline groups. 
E. C. 
Wasnuineton, D. C., September 9th, 1872. 
