HISTORICAL PREFACE. 
xxix 
and throughout the work have analyzed species under their respective genera, these 
under their subfamilies or families, and these again under their orders. 
Part IV. consists of a Synopsis of the Fossil birds of North America, corresponding 
to the appendix of the old " Key," but augmented by later discoveries. As before, this 
part of the work has been revised by Professor 0. C. Marsh. 
In the mechanical execution of the work, it has been my aim to compress the most 
matter into the least space and leave no waste paper, in order to keep the treatise within 
a single portable volume of convenient text-book size. I judge that there is nearly four 
times as much matter in the present volume as there was in the original edition, the 
page being much more closely printed, in a smaller type, and on thinner paper. 
The old " Key " was insufficiently illustrated, and the average character of the cuts 
was not entirely satisfactory. The present edition more than doubles the number of 
illustrations. These are in part original, in part derived from various sources, all of 
which are duly accredited in the text. The basis of the series is of course the cuts of the 
former edition ; but many of these have been discarded and replaced by better ones. 
About fifty of the most effective engravings were secured by my publishers from Brehm's 
Tliierleben ; " nearly as many more are from Dixon's " Rural Bird Life," the American 
edition of which is owned by the same firm. A few have been copied from D. G. Elliot's 
" Birds of America," and a few others from the Proceedings of the Zoological Society of 
London. About fifty of the prettiest ones were drawn by Mr. Edwin Sheppard and en- 
graved by Mr. H. H. Nichols, expressly for this edition, xinother set' — how many there 
are of them I do not know — are from my own drawings, and have mostly appeared in 
other of my publications. Several of Mr. R. Ridgway's drawings have been placed at my 
service, through his kind attentions, and with Professor Baird's permission. I am in- 
debted to Dr. R. W. Shufeldt, U. S. A., for about thirty original anatomical drawings, as 
well as for the colored frontispiece. Mr. Henry W. Elliott has kindly put at my dis- 
position several of his own artistic compositions, and I have received some very beautiful 
engravings with the compliments of the Century Company of New York. 
It is always agreeable to pay one's respects when due, and acknowledge assistance 
and encouragement received in the preparation of one's books. Yet what an embarrass- 
ment is mine now ! For there is no writer of repute on North American ornithology, 
and scarcely a leader of the science at large, who has not assisted in the making of the 
" Key ; " and there is no reader of the work who has not encouraged its author to produce 
this new edition. I am trebly in debt, — to thousands whose names I know not ; to 
hundreds I only know by name and fame ; to scores of tried and trusted friends. 
But let me say how much I am indebted to my compositors and proof-readers of the 
University Press at Cambridge for the skill with which they have turned copy into print, 
and to the proprietors of that justly-celebrated establishment for the pains they have 
taken in making the book an example of beautiful and accurate typography. Let me 
recognize here the liberality and generosity of my friend, Mr. Dana Estes, senior of the 
firm of Estes and Lauriat, in permitting me to make the book to suit myself, and in 
sparing no expense to which he might be put in consequence. Let me not forget that 
during its preparation, as for many years previously, I have enjoyed to the fullest extent 
the privileges of the Smithsonian Institution and the National Museum, through the 
courtesy of Professor Baird, my access to the great collection of birds being always facili- 
