PREFACE. XI 
the Ray Society and of the public. Any person who has 
access to periodical works, whether British or foreign, which 
appear to have been unnoticed by the compilers of the pre- 
sent Catalogue, will confer a boon by extracting the titles of 
the zoological and geological papers which they contain, re- 
ferring to the volume and page of the original work, in the 
form adopted in this volume. The titles of such Books also 
as have been omitted in our list, or have been published sub- 
sequently, especially those of rare provincial and otherwise 
inaccessible tracts and pamphlets on Zoology or Geology, 
will be exceedingly acceptable. All such titles should be 
written on one side of the paper only, and may be addressed 
to the Secretary, Dr. E. Lankester, 22 Old Burlington Street, 
London. 
I wish it had been in my power to have given an exact list 
of those periodicals, the titles of whose contents have been 
wholly or partly extracted into this work, so that those who 
are disposed to aid in the above object might at once see 
whether any given periodical had already been made use of 
or not. Unfortunately M. Agassiz omitted to keep such a 
list; and to enumerate those which have been consulted by 
myself would have only partially remedied this defect. By 
referring however to a few of the individual titles, as entered 
in this volume, it will easily be seen whether the work in 
which they are contained has been systematically consulted 
or not; and the List of the Abbreviations employed will also 
assist this object. 
A person who was willing to devote his life to compilation 
might no doubt have made this work more convenient for 
some purposes by arranging it as a classed instead of an 
alphabetical catalogue. Such a task was not, however, practi- 
cable in the present case, but every one may to a certain ex- 
tent make it into a classed catalogue for himself, by attaching 
