iv PREFACE. 
arrangement, Probably the next step in perfecting this system will 
be marked by a consideration of the larval stages, the knowledge 
of which, at present, is so very fragmentary. 
On comparing the two editions a great improvement will be 
found in the series of specimens, which, for many years, have been 
selected with the view cf illustrating the geographical range of the 
species. Specimens with uncertain localities or without known 
origin, if no other special interest was attached to them, and espe- 
cially duplicates, have been eliminated from the collection. 
Thus the present work, although it appears in the list of publica- 
tions of the British Museum as a “second edition,” is almost entirely 
original. It has been prepared by M. Boulenger, Aide-Naturalist 
in the Royal Belgian Museum; and I feel confident that zoologists 
will thankfully acknowledge the industry and ability with which 
the author has performed the difficult task entrusted to him by the 
‘Trustees. 
ALBERT GUNTHER, 
Keeper of the Department of Zoology. 
British Museum, 
February 1, 1882. 
