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THE great attention paid to the British land and freshwater shells by Montagu; by my late friend and teacher in zoology, Dr. Leach; and more recently by Mr. Jeffreys, Mr. Jenyns, and Mr. Alder (more especially the latter), has left me little else to do, in revising this edition, than to embody their observations. This is the more peculiarly the case, inasmuch as they all, in a great measure, worked from the collection now under my charge, which contains the materials used by Dr. Leach in preparing his as yet unedited work on British Mollusca, and, among the rest, the various specimens which I had myself collected when actively engaged in the study of our British species. It is right, however, to add, that, before adopting the remarks of these authors, I have, in every instance where it was in my power (and that was almost universally), verified the facts myself; and, therefore, although I have used their words, from


a desire to do justice to their labours, the conclusions are most frequently equally my own.

In determining the names of the species, I have always acted on the only certain and just rule, — that of priority, unless the name first used was decidedly objectionable, on account of its giving an incorrect idea. In so doing, I have been obliged to change some of the names employed by Mr. Alder and Mr. Jeffreys, who, from a desire to make our Fauna agree with the continental works which they have studied, have been induced to adopt several of the names given by French authors, although long posterior to those applied to the same species by our own most accurate observer and describer, Montagu. The work of this excellent zoologist (when we consider the period of its publication, and the difficulties which the author had to encounter from the prejudices then in force) deserves to be placed in a very high rank; and the marked attention which he paid to the animals of the species that had come under his observation proves that his views were far superior to those of his age. Mr. Alder gives as his reason for adopting these more modern French names in preference, that they are almost exclusively used on the Continent-by which, I presume, he means in France; for, if we study the works published in different European countries, and especially their Faunas, we shall find that each of them has its own peculiar favourite, whose arrangement and nomenclature the naturalists of that country are most inclined to adopt. Thus, though the names given by Draparnaud are commonly used in France, those of Müller are almost exclusively adopted in Germany

and Sweden; and the authors of the latter countries would as readily have adopted the names of Montagu as those of Draparnaud, if they had been acquainted with the work of the former, which, it should be recollected, was published at a period when we were excluded from the Continent by an unhappy war.

It ought to be, and, judging from the attention which our botanists and zoologists pay to continental works, I believe it is, the desire of the naturalists of this country to give to each author his just due, let him belong to what country he may; and, eventually, this high position must be taken even by those (if any such there be) who are now restricted by narrow national prejudices from consulting the works of their contemporaries in other countries. It is these considerations which have induced me to take the course I have adopted. I believe, moreover, that if I had followed that recommended by Mr. Alder and Mr. Jeffreys, I should have experienced continual difficulties in determining whether the name of a species used by German or French authors was the most generally adopted; and this difficulty would have gone on daily increasing, inasmuch as the Germans are paying more and more attention to natural science, and their language is becoming more generally studied in this country.

A short description of the animals, and a few notes on their habits, have been added; and this new feature in the work might have been greatly extended, had it not been feared to add too much to its bulk.

Great care has been taken in correcting such false impressions as may have been produced by oversights in the works of preceding English writers on

the subject, and reference has been made to such of their observations as have appeared to be of sufficient importance to find a place in a work which is intended only as a manual for the student. One animal of each of the more typical genera of each of the families has been figured, and new plates have been added, containing the species not before figured, together with figures and details of some of the smaller species, which were not executed so well as might have been wished in the preceding edition.

Wishing to make the work really what its title represents it, the species described are restricted to those which appear to be truly native, and only the two following, viz.—

Testacella haliotoidea, t. 3. f. 19., and

Driessina polymorpha,

have been admitted among those which are supposed to have been introduced in modern times. These have been admitted, because they have become truly naturalised, and propagate themselves in our climate in the open air. Indeed it is doubtful whether the first of them may not be as truly native as several other species commonly considered so; such as, Helix Pomatia, H. holosericea, H. limbata, H. Carthusiana, and H. Pisana. Several other species were recorded and described in the first edition of this work, which have been introduced with foreign plants, either buried in the mould, or on the plants themselves, or which have most probably been brought to this country in the egg state. These are not truly acclimatised, and only propagate their species when they are kept in stoves or hot-houses; they can therefore have no pretension to be considered as natives: among them must be recorded, the

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