BRITISH MAMMALS. 



INTRODUCTION. 



ACCORDING to the admirable classification proposed by Dr. 

 A. R. Wallace, the British Islands come under the category of 

 " Continental " Islands ; that is to say, they are islands of large 

 size, composed to a great extent of sedimentary rocks, and 

 situated near to a continent, with the fauna and flora of which 

 their own animals and plants agree to a greater or less extent. 

 Many islands of this class have evidently been united to the 

 continents to which they are adjacent, at no very remote 

 epoch ; and this is attested in our own case not only by the 

 shallowness of the English Channel and the North Sea, but 

 likewise by the similarity of the geological formations on the 

 two sides of the Channel, as well as by the fact that there is 

 not a single indigenous species of British Mammal that is not 

 likewise met with on the Continent. That there are certain 

 continental Mammals now unknown in a living condition in 

 our islands is, indeed, true, but of this we have an adequate 

 and sufficient explanation. Before discussing this point it may, 

 however, be well to mention that the second group of islands 

 in Dr. Wallace's classification are termed " Oceanic " Islands. 

 These are generally of small size, situated either in mid-ocean, 

 where they rise abruptly from great depths, or, if near to a conti- 

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