THE BRITISH WATER RAT 479 



(Celtic) : — Scottish Gaelic — radan-uisge = " water rat" (C. H. Alston) ; 

 lamhalan, perhaps from famh-alan = " water mole." Welsh — llygoden 

 y dwfr ="'^3Xer rat" (Forrest). 



In general appearance and characters the British Water Rat is 

 typical of the genus Arvicola ; in size it is larger than other European 

 species, excepting A. sapidus. The tail is somewhat more than half as 

 long as the head and body. As compared with Epimys norvegicus it 

 has the body heavier and more robust, the tail relatively shorter, and the 

 head distinctly more rounded. Although the ears (PI. XXVI., Fig. i) 

 are well developed, they are inconspicuous, barely show above the fur, 

 and when laid forward hardly reach half-way to the eyes. They are 

 on both surfaces thinly clothed with rather long hairs, subcircular in 

 outline, and with well-developed, bluntly triangular, naked meatal valves. 

 The small eyes lie about half-way between the ears and the muzzle. 

 The nostril-pad is small and naked, its lower border continuous with 

 the naked median groove of the upper lip. The upper incisors project 

 slightly when the mouth is closed. 



The hands are broad and robust, but not specialised in any particular 

 direction ; the rudimentary thumbs are smaller than the smallest palmar 

 pads, but carry distinct nails covering their dorsal surfaces ; digit three 

 is longest, slightly exceeding four, as four does two, five reaching about to 

 the base of four ; all the digits are scaled on their under surfaces, and 

 carry slender slightly curved claws, equal in length to about one-quarter 

 of their digit. 



The feet are large and slightly fringed, apparently for swimming; 

 of the digits the first is smallest, reaching about half-way to the base 

 of the second; the second, third, fourth, and fifth are much as in the 

 hand, as are the scales and claws, the latter, however, stronger than in 

 the hand ; except for a slight sprinkling of hairs on the posterior third, 

 the soles are naked. The pads are variable both in size, and, 

 sometimes, in number, being evidently in course of reduction. As a 

 rule they are comparatively small, and the small internal proximal one 

 appears only as a smooth spot, so that the total is normally five, 

 but occasionally six are present. In one specimen the feet 

 showed a confused mass of tumid flesh without true differentiation 

 into pads. 



The tail tapers noticeably from a thick base ; when laid forward it 

 reaches about to the shoulders or slightly beyond ; the annulations are 

 irregular, but clearly visible and not concealed by the hairs — about 1 5 

 to the centimetre at the middle of the tail. The numerous hairs are 4 to 

 5 mm. long and form a slight terminal tuft 



The mainmsB are as in Microtus. 



There are on the flanks, about half-way between the root of the tail 

 and the scapulae, paired vascular glands, oval in structure (17x12 mm. 



