v1 PREFACE. 
solved on proposing such terms to M. Agassiz as induced 
him to make over to the Society the whole of his materials. 
Having been requested to act as Editor of the work, and 
having been in the habit of compiling for my own use a simi- 
lar, though less extensive, Catalogue of Zoo-bibliography, I 
am enabled to make numerous additions and corrections to 
the labours of M. Agassiz and his coadjutors. I have also 
consulted various published lists, and have derived much as- 
sistance from the very useful “ Verzeichniss der Biicher tiber 
Naturgeschichte,” lately published by Engelmann. To Mr. 
J. EK. Gray also I am indebted for the use of a MS. catalogue 
of entomological works compiled some years ago by Mr. 
Bennett and himself. I am well aware that a Catalogue 
which is intended to include all that has ever been published 
on so extensive a subject, must necessarily be very defective 
both in completeness and accuracy; still, so far as it goes, 
there can be no doubt of its utility ; and if the work be found, 
as I trust it will, to be by far more extensive and correct 
than any of its predecessors, the Ray Society will have no 
cause to regret the undertaking. 
The greatest difficulty which has been felt in making this 
compilation, has been to define the limits by which to cireum- 
scribe it. So intimately connected are the several sciences, 
that bibliographers well know the difficulty of making a satis- 
factory classification of books according to their subject- 
matter, and the same impediment is equally felt in making 
lists of works which shall exhibit the whole, and nothing but 
the whole, of any given department of knowledge. In the 
present case, the primary object of M. Agassiz was to insert in 
his Catalogue the titles of every work and essay on ZooLocy, 
as a science of observation and of classification. The Zoology 
of past epochs, as well as of the present, necessarily formed 
an element in this design, and hence it was necessary to in- 
