ii PRErACE. 
contains a complete list accompanied by accurate descriptions. The absence of coloured 
illustrations and the additions of the last seven years to the family since its publication, are 
the only reasons which justify the preparation of another monograph whilst the former is in 
existence. 
The compilation of a work of this nature sufficiently accurate to be of any assistance to 
science, could only be carried out by obtaining the cooperation of the leading naturalists 
themselves, and the aid afforded by collections and libraries ; any measure of success that 
we may attain to in our object will be due to the cordial support we have received on all 
hands. The valuable private collections of Lord Walden, Messrs. Eyton, Sclater, Salvin, 
Sharpe, and Wallace have been placed at our disposal ; and these, together with our own 
collection, the public collections of London, Leiden, Amsterdam, and Liverpool, and the 
library of the Zoological Society of London, have supplied us with almost all the necessary 
materials for our work. Dr. Hartlaub, of Bremen, Dr. Peters, of Beriin, and Dr. Salvadori, 
of Turin, have also kindly aided us ; but most of all we are indebted to Professor Schlegel, of 
Leiden, for his courtesy iu permitting us to take to England, to figure, several rare and 
unique birds, without which we should have found it difficult to complete the work. 
The execution of the plates has been entrusted to Mr. J. G. Keulemans; and the 
accuracy of their execution will increase the value of the book. Many of the Barbets are 
here figured for the first time, while of some others the only drawings extant are in the 
older authors, such as Le Vaillant and BufFon, which do not come up to the standard 
required now. 
No labour has been spared to render the work as perfect as possible, and every available 
source of information has been laid under contribution ; but as the science is a progressive 
one, new matter may probably come to light during the course of publication. To meet this 
difficulty a short appendix will be added, which it would be desirable in all cases to refer to 
before determining any thing from the body of the work. 
Mr. R. B. Sharpe, the author of a ' Monograph of the Alcedinidae,' has assisted us 
greatly in editing the work, in which his experience has been valuable. There are a few 
errors to be found in the letterpress, unavoidable in a work of this kind ; but care has been 
taken to reduce them to a minimum. 
The collection of birds which forms the basis of this work is now in the possession of the 
Marquis of Huntly, at Aboyne Castle. 
