244 BRITISH MAMMALS 



Mus sylvaticus. THE LONG-TAILED FIELD MOUSE 



This ofttimes very beautiful little creature (though some of 

 its varieties are markedly prettier than others in coloration and 

 form) is frequently confused with the common house mouse by 

 unobservant people. It resembles the last-named mouse closely 

 in form and shape, but the tail is proportionately longer, 

 measuring exactly the same as the head and body. Each of 

 these measurements is about 4 in. in average specimens. It 

 is thus in most of its sub-species a larger animal than the 

 common mouse. In an admirable paper on Mus sylvaticus 

 and its allies (published in the Proceedings of the Zoological 

 Society, April, 1900), Mr. G. E. H. Barrett Hamilton recognises 

 nineteen sub-species or varieties of Mus sylvaticus, the forms at 

 either end of this series differing widely in appearance, in colour, 

 and in size. Of these, five inhabit different parts of Great 

 Britain and Ireland at the present day, while osseous remains 

 have been collected in Kent, which would seem to indicate the 

 former existence of a sixth sub-species. The typical length of 

 the field mouse (or wood mouse, as it is sometimes called) is, 

 as already stated, in excess of that of the common mouse. 



The preponderating number of sub-species have a handsome 

 and well-marked coloration, which is warm reddish-brown or 

 yellowish-gray above and pure white below, with a brown or 

 yellow spot in the middle of the chest. The demarcation 

 between the white of the under parts and the sandy-red of the 

 upper is, in most varieties, very abrupt. The white of the 

 under part includes the inside aspects of the limbs and the outer 

 aspects of the paws, and extends across the cheeks to the tip of 

 the nose. The under side of the tail is also pure white. The 

 large, broad, rounded ears are hairy on the outer side and some- 

 what naked within, though in the inner aspect there are sparse, 

 long hairs. The vibrissae, or whiskers, are very long, and the 

 eyes are particularly large and prominent. The five varieties 

 which are found in the British Islands are named, distinguished, 

 and distributed as follows : 



