INTRODUCTION. 
In describing several new species of Tortricidce from North America, and re- 
describing such of Mr. Walker's species as had not been anticipated by other 
authors, and of which the types are now in the British Museum, I have thought 
it advisable to adopt as far as possible the system of classification laid down by 
Heinemann in his ' Schmetterlinge Deutschlands und der Schweiz,' published 
in 1865. 
Many systems of generic subdivision have been suggested for this difficult 
group ; but all appear to have been founded upon a study of European species 
only. So far as I have been able to judge, none of these various systems are 
sufficiently perfect and natural to facilitate the arrangement of a cosmopolitan 
collection. It is very desirable that some comprehensive system should be 
devised ; but for this purpose a very careful study of specimens from all parts 
of the world is obviously necessary, and it may be long before such a work can 
be successfully undertaken. Until this has been done, any arrangement of this 
group of insects must, I think, be considered, in part at least, provisional. 
In the meanwhile Heinemann's system, although not infallible when applied 
to large numbers of species with which he was necessarily unacquainted, seems 
to afford a wider and sounder basis for generic classification than those of other 
authors. He attaches much value to diff'erences of neuration ; and although 
