The specific characters, which are for the most part entirely new, have been drawn up, as far as practicable, with a view to the exact differences of species; but the difficulty of doing this in the instance of the aquatic Birds, which are subject to such great changes of plumage from age and other circumstances, it must be confessed is very great, and has not in all cases been satisfactorily got over. In the Class of Fish, specific characters have seldom been added in the case of genera or sub-genera containing not more than one British species, or when given, bear reference solely to other, nearly allied, European species; the essential characters of those met with in other countries, in many groups, not having been hitherto determined with precision.

The terms employed in characterizing the larger groups, or in drawing up the descriptions of species, have for the most part been derived from the works of Illiger *, Des-marest †, and Cuvier. The "Histoire Naturelle des Pois-sons" of this last author has been exclusively resorted to in the Class of Fish. To these works, the reader, to whom the terms are not familiar, is accordingly referred.

* Prodromus Systematis Mammalium et Avium. Berol. 1811. 8vo. This work will be found to contain a very complete terminology with reference to the two classes of Mammalia and Birds.

†Terminologie des Marnmiferls ; prefixed to his " Mammalogie".

On the subject of Nomenclature it may be remarked that the oldest names have been adopted in most instances, unless a different one has been sanctioned by general use. As the author is of opinion that in common parlance there is no occasion to name the sub-genus, when speaking of any particular species, he has not thought it necessary to change the names of species which are the same as those of the sub-genera to which they belong.

The synonyms will be found to embrace references to some of the principal writers, more especially those in our own country, who have treated of the different Classes, or of any subordinate group, or any particular species. These references have, in every instance, been examined personally by the author. To facilitate the inquiries of such persons, as may wish to examine for themselves on this subject, a complete list has been annexed of all those works, with their several editions, which are quoted, either for the synonyms, or for any other purpose.

It has been thought proper to annex two distinct indexes, one containing the Latin, the other the English names. No pains have been spared to render them as complete as possible. It is believed that every name and synonym, in the above two languages, occurring in the body of the work, will be found in its proper place.

It now only remains for the author to express his acknowledgments to those friends who have assisted him in this undertaking. To Mr. Yarrell in particular, he begs publicly to return his sincere thanks for the able help which he has experienced at his hands, and such as alone has enabled him to complete the work upon the plan first contemplated. This help has been especially felt upon the subject of the British Fishes. Had it not been for the very liberal manner in which that gentleman offered him the almost unlimited use of his Manuscripts and rich collections, the author has no hesitation in saying that he could never have extended the Manual to that department, or presumed to enter upon a field, to which he was previously almost an entire stranger. Assistance, however, has been not the less afforded him in the other Classes. Mr. Yarrelfs well-known practical acquaintance with our British Birds has enabled the author to detail more at length the changes of plumage to which some species are liable, and to correct a few errors into which previous writers had fallen on this subject. The same gentleman kindly volunteered an accurate description, accompanied by measurements, of the egg of every species, of which his extensive collection afforded specimens; thus enhancing the utility of the work by an addition, which, but for this circumstance, the author would have been unable to supply. He begs it may be distinctly understood that this portion of it is from the pen of Mr. Yarrell.

To Mr. Gray, he desires to make an acknowledgment of the readiness with which he has at all times allowed him to consult the specimens in the British Museum. The same return must be made to the officers of the Zoological Society for similar liberty to examine a few specimens contained in their collection.

In conclusion, the author may state that he has no intention of extending his work to the Invertebrate Division of the British Fauna. In the present advanced state of the Science, a complete Manual of all the Animals occurring in these Islands can only be accomplished by the united labours of many individuals. With the view, however, of continuing his researches into that portion of it which is here treated of, he begs to solicit such observations, notices of new or rare species, and, where it may not be inconvenient, specimens, as it may be in the power of any of his readers to supply. Even the Vertebrate Animals of our own country are far yet from being thoroughly understood. Much confusion prevails in several groups, and, without doubt, many additional species remain to be detected. The Shrews and Bats amongst Quadrupeds; the Cetaceous Animals; the Wrasses, Gobies, Blennies, the Salmon Tribe, the Sharks and Rays, amongst Fish; these and other families might be pointed out, with respect to which we want more information, and which particularly invite the attention of the British Naturalist. Should any one be disposed to honour him with specimens in these or other instances, the author begs to state that they will not be reserved for his own use exclusively, but will, with the permission of the donor, be deposited in the Museum of the Cambridge Philosophical Society, which already possesses an extensive collection of British Animals, and which the author is anxious to render as perfect as possible in that department of the Fauna, to the advancement of which the Work now offered to the Public is directed.

SWAFFHAM BULBECK,

Oct. 24, 1835.

The Author takes this opportunity of expressing his grateful acknowledgments to the Syndics of the University Press, for their liberality in taking upon themselves the expense of printing this Work.