The present Work contains descriptions of all the Vertebrate Animals, including the domesticated, naturalized, and extirpated species, which have been hitherto observed in the British Islands. The object of its author is to present Naturalists with a Manual in this department of our Fauna, adapted to the existing state of our knowledge, and such as shall be calculated to meet the wants of the Science in that advanced stage to which it has attained since the publication of former works of this nature. In furtherance of this end two points appeared necessary to be attended to. One was to ascertain, as far as practicable, the additions which had been made of late years to our lists of British Animals, to inquire into the respective claims of those which had been admitted into these lists previously, and carefully to distinguish between such species as have unquestionably occurred within the limits of our own Islands, or in the adjoining seas, and others of which reasonable doubts might be entertained in reference to this matter. The other important point, as it appeared to the author, was to take care that the descriptions should as far as possible be obtained from the animals themselves, and nothing inserted upon the credit of other writers which was capable of being verified by personal examination. The day is for ever gone by in which mere compilations will be thought to be of any service to the science of Zoology. So far from advancing its progress, it may be said unhesitatingly that they tend only to retard it. It is through such channels that errors already of long standing become more widely circulated, at the same time that new ones, to a greater or less extent, are infallibly introduced. The author who is too indolent to examine and describe for himself, has often spared himself the trouble of even investigating the nature of the materials which he has obtained from others. The consequence is, that he has perhaps blended together the descriptions of two or more perfectly distinct species, or out of one made several, or, led away by the identity of mere names, has transferred to our native animals the descriptions of exotic, nearly allied species, with which he has confounded them.

After the above enunciation of the two leading points which have been borne in mind whilst preparing this work for publication, the author hopes that it will not be thought uncalled for by those for whose use and guidance it is principally intended. The latest previous work upon the same subject and conducted upon the same general plan is the "History of British Animals'" by Dr. Fleming. This was completed in 1827 and published the year following, since which period a great variety of species have been added to the Fauna of this country, more particularly in the Class of Fish, though many occur in the Classes of Quadrupeds and Birds. As these additions have been already indicated in the "Systematic Catalogue'" lately published by the author of the present work, it is unnecessary to dwell upon them individually. It may, however, afford interest to present a comparative view of the aggregate numbers of species in each Class, as they appear in the "British Animals" of Dr. Fleming and in the Manual now offered to the public.

The total number of Mammalia noticed by that Naturalist, excluding the domesticated and naturalized species, as well as all those not met with at the present day, is fifty-three, from which deducting three as of rather doubtful character, there remain fifty. The number of Birds, excluding in like manner the domesticated and naturalized kinds, but including Stragglers, which Dr. Fleming has only briefly alluded to and not allowed to form part of the regular numbering, amounts to two hundred and eighty-one, from which deducting seventeen as either decidedly not British or of doubtful character, there remain two hundred and sixty-four. The number of Reptiles and Amphibious Animals, which are united in one Class, is fourteen, from which deducting one as a doubtful native, and two others as very doubtful species, there remain eleven. The number of indigenous Fish amounts to one hundred and seventy, from which deducting eleven not distinct from others, one not British, and three of doubtful character, there remain one hundred and fifty-five, which added to about seven noticed only as stragglers*, gives one hundred and sixty-two. Hence it appears that the total number of truly British Vertebrata, restricting the expression in the manner above indicated, described or mentioned by Dr. Fleming, amounts to only four hundred and eighty-seven. In the present work, excluding in a similar way the domesticated, naturalized, and extirpated species, as well as all those of doubtful character, the number of described Mammalia amounts to sixty-one; that of Birds to two hundred and ninety-seven; that of Reptiles and Amphibious Animals together to thirteen; that of Fish to two hundred and ten. These added together give five hundred and eighty-one as the total number, exceeding that above stated by ninety-four. But independently of these additions which have been made of late years to our native Animals, Dr. Fleming's work professing to be in a great measure only a compilation, it was thought that one which partook more of an original character, would not prove unacceptable at the present day. It must not be forgotten that two other works connected with the Vertebrate" Division of the British Fauna have appeared since the one just spoken of. I allude to the excellent "Illustrations of British Ornithology" by Mr. Selby, published in 1833, in which the number of Birds is raised to two hundred and eighty*, and the valuable "British Fishes" of Mr. Yarrell now in course of publication. But not to dwell upon the circumstance, that these works are upon totally different plans from that of the present one, the author conceives that a single volume comprising all the Vertebrate Animals which have been observed hitherto in these Islands will form a useful addition to the library of the British Naturalist, as well as prove a convenient travelling companion.