XXIV INTRODUCTION. 
upheld upon fixed principles by such rules as those above 
mentioned. In the present case, therefore, an attempt has 
been made to rectify the nomenclature of all the species which 
have found their way into the British list, by presenting the 
reader with the oldest, as far as could be ascertained, and 
therefore the most correct name for each, coupled with the 
name of the author who first bestowed it. 
The same principle has been applied, although less satis- 
factorily, to genera; and, for the sake of simplicity, the adop- 
tion of subgenera has been as much as possible avoided. It 
may be further observed that, although in the main the syste- 
matic arrangement here followed is that adopted by Yarrell, 
it has been deemed expedient to introduce therein certain 
modifications which have become necessary from an extended 
knowledge of the species dealt with. The Orioles, for ex- 
ample, as also the Rock Thrushes, have been separated from 
the true Thrushes, with which Yarrell had associated them. 
The Tree Creeper and Common Wren, hitherto placed 
amongst the Scansorial birds in company with the Wryneck 
and other zygodactyle forms, have been removed to a position 
more in accordance with their structure and habits. The 
Plovers and Sandpipers, between which families Yarrell in- 
terposed the Cranes, Herons, and Storks, have been brought 
into close proximity from a due consideration of their natural 
affinities ; and in a similar manner other families and genera 
have been dealt with. In all cases where Yarrell’s work is 
quoted, the pages indicated are those of the 3rd and last 
edition of 1856, the publication of the 4th edition by Pro- 
fessor Newton having only recently commenced. 
In conclusion, it may be observed that, as the present work, 
from its nature, cannot be expected to be free from mistakes, 
any corrections or emendations which may be communicated 
by the reader will be gratefully received by the author. 
