CONTENTS. Page PREFACE BY THE EDITOR. THE voluminous work which the RAY SOCIETY has here undertaken to publish, has been mainly compiled by Professor Agassiz, during the leisure moments of a life of almost incessant scientific research. Originally prepared for his own private use as an index to the numerous works on Zoology and Geology which he had occasion to consult, the collection gradually increased upon his hands, and the importance of its publication as an aid to other scientific investigators became daily more evident. Not trusting however to the means within his own reach, he established an extensive correspondence with naturalists in all parts of Europe, from whom he received an immense addition of materials on the scientific bibliography of their respective countries, and he was thus enabled to prepare a catalogue,—not indeed a complete one, for that can never be attained in practice, but far more perfect than any existing, of all known works and detached memoirs on Zoology and Geology. The utility of such a work to the scientific student is sufficiently evident, yet its technical nature rendered its publication a matter of very doubtful policy to one who could ill afford to sustain a probable loss. The work might therefore have been indefinitely delayed, or never have seen the light at all, were it not for the intervention of the RAY SOCIETY, whose Council were so convinced of its value, that they re 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 similar, 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 assistance from the very useful "Verzeichniss der Bücher über 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 circumscribe it. So intimately connected are the several sciences, that bibliographers well know the difficulty of making a satisfactory classification of books according to their subjectmatter, 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 |