iv TEEFACE. 



arraugement. 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 of 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-lfaturalist 

 in the Eoyal Belgian Museum ; and I feel confident that zoologists 

 will thankfully acknowledge the industry and abihty with which 

 the author has performed the difficult task entrusted to him by the 

 Trustees. 



ALBEET GUJs'THER, 



Keeper of the Dej^ariment of Zooloc/y. 



British Museum, 

 February 1, 1882. 



