6 The Genera and Species of Mallophaga 
as a basis for future revisions; and on this point I have a little more to 
say later on. 
The number of specific names given in the list is 2395, of which 
1520 are treated as valid, and 875 as invalid. 
(vi) Bibliography. This does not purport to be a complete biblio¬ 
graphy of Mallophaga, nor does it include anything like all the works 
examined in the preparation of this List. But it does include all the 
works with which I am acquainted, or to which I could find references, 
which deal with systematics and nomenclature. A considerable number 
of these are here quoted for the first time. Thanks to the courtesy 
and kindly assistance of the library staffs at the Cambridge University, 
Cambridge Philosophical Society, and the British Museum (Natural 
History) Libraries, I have personally studied all these works, with 
only one or two exceptions. 
(vii) List of new names introduced in this publication. Owing to the 
inclusion in my list of a large number of synonymical names, a number 
of current names for species are shown to be invalid. For these I have 
been obliged to put forward new names, which are distinguished by 
an asterisk in the list itself; but which I have brought together under 
this heading for the purpose of affording more convenient reference. 
(viii) Index to genera. This hardly demands explanation. It 
applies only to the List of Specific Names, and is included to facilitate 
reference. In the other lists, Sections ii and iii, names are in alphabetical 
order; and the same holds for the species included under each genus 
in Section v; so that a multiplication of indices has seemed to me 
unnecessary. 
Having made a complete survey of the systematic work upon 
Mallophaga up to the present, I may perhaps be permitted to set upon 
paper a few thoughts as to this work in the future. In the course of 
my somewhat tedious labour, I have been appalled at the number of 
species which must for the present be allowed to stand as valid, but 
which will never be really recognised until either the types have been 
examined and carefully redescribed, or fresh material from the same 
host has been critically examined and dealt with. If we are to avoid 
a continuation of this state of affairs, it seems to me that it will be 
necessary to establish definite criteria upon which specific descriptions 
may be based. This is hardly a matter for an individual worker, but 
it should be possible to arrive at some decision after an informal dis¬ 
cussion among the specialists at present working on the group. The 
few points which I put forward in the next paragraphs are simply tenta¬ 
tive suggestions, and are the outcome of my own gropings after light. 
