IV PREFACE. 



shortly be able to complete his monograph of the uEschninee, of 

 which he has already published the synopsis of genera^ and 

 which will add at least one third to the number of species 

 already described in that subfamily. 



I am indebted to Mr. S. H. Scudder for furnishing me with 

 some additions to the list of Fossil Odonata in Appendix I. 

 (including species about to be published in his forthcoming 

 treatise on the Tertiary Insects of North America), and to 

 Mr. C. Davies Sherborn for looking over the MS. and proofs of 

 the same part of the Catalogue. 



In Appendix II. will be found omissions; additions made to 

 the subject during the progress of this work through the press ; 

 and any recent corrections of importance which I have noticed, 

 or to which my attention has been called, and which I have 

 found, on examination, to be well-grounded. The student is 

 recommended to take special note of this Appendix when 

 making use of the book. 



I need say nothing of the merits or demerits of the Catalogue 

 itself, of which those who use it will form their own opinion ; 

 but it may be desirable to make some observations on the 

 principles of nomenclature which have been adopted, after full 

 consideration and much experience of work of this nature. 



I find that initiid capitals catch the eye so much more readily 

 than small letters, that I make no apology for employing them 

 for specific names throughout (contrary to the usual practice) 

 in all works for the technical details of which I am personally 

 responsible. It might also be argued that the binomial names 

 of species are practically equivalent to proper names. 



The nomenclature is made to commence from the 10th edition 

 of Linne's ' Systema Naturae' (1758). The starting-point of 

 the 12th edition (1767), fixed by the British Association Rules, 

 is invalidated by their admission of exceptions. The Linuean 

 system was practically established in 1758, and was adopted by 

 most naturalists of repute between 1758 and 1767; nor can we 

 always determine Linne's own species described in 1767 without 

 reference to the more detailed descri])tions or figures published 



