VI 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 iiber 

 Naturgeschichte," lately published by Engelmann. To Mr. 

 J. E. 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 circum- 

 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 ZOOLOGY, 

 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- 



