ADVERTISEMENT. 
When I presented my collection of Birds to the Zoological Society, Mr. 
Gould kindly undertook to furnish me with descriptions of the new species and 
names of those already known. This he has performed, but owing to the hurry, 
consequent on his departure for Australia, — an expedition from which the science 
of Ornithology will derive such great advantages, — he was compelled to leave 
some part of his manuscript so far incomplete, that without the possibility of 
personal communication with him, I was left in doubt on some essential points. 
Mr. George Robert Gray, the ornithological assistant in the Zoological depart- 
ment of the British Museum, has in the most obliging manner undertaken to 
obviate this difficulty, by furnishing me with information with respect to some 
parts of the general arrangement, and likewise on that most intricate subject, — 
the knowledge of what species have already been described, and the use of proper 
generic terms. I shall endeavour in every part of the text to refer to Mr. G. R. 
Gray’s assistance, where I have used it. As some of Mr. Gould’s descriptions 
appeared to me brief, I have enlarged them, but have always endeavoured to retain 
his specific character; so that, by this means, I trust I shall not throw any 
obscurity on what he considers the essential character in each case ; but at the 
same time, I hope, that these additional remarks may render the work more 
complete. 
The accompanying illustrations, which are fifty in number, were taken from 
sketches made by Mr. Gould himself, and executed on stone by Mrs. Gould, with 
B 
