400 MICROTIN.E 



mg is a very prominent feature of tlie inner surface of the jaw. 

 Incisors large but normal. Cheek-teeth robust ; enamel pattern 

 (Fig. 109) normal as described above under the genus; m^ and 

 m^ with ephemeral complications in youthful stages of wear. 



Geographical differentiation. — Two subspecies of A. amphibius 

 are currently recognized, viz. (1) the typical form inhabiting 

 England and Wales and the Lowlands of Scotland, characterized 

 by lighter brown colour and large size, and (2) A. a. reta, a 

 darker and apparently smaller form inhabiting the Highlands of 

 Scotland beyond the Clyde and Tay watersheds. Melanism is 

 frequent in A. a. reta, comparatively rare in A. a. amphibius; 

 but in the eastern counties of England (Cambridge and Norfolk) 

 there are colonies of black water-voles, the exact status of which 

 is at present doubtful. 



Although the habits of this animal are chiefly aquatic they 

 are by no means exclusively so. It is a powerful digger, and many 

 of the chief modifications seen in its skull, dentition and feet are 

 expressions of fossorial and not of aquatic specialization. It may 

 be taken high up on hills or on sandy wastes far removed from any 

 stream or standing water. Like most other Muridse it will in 

 certain circumstances invade human dwellings. I once killed 

 one accidentally in a cottage in Kent more than a mile distant 

 from a brook. 



5ff. Arvicola amphibius amphibius Linnaeus. 

 1758. Mus amphibius Linnaeus, Syst. Nat., ed. 10, 1, p. 61. 

 1817. Lenimus aquaticus F. Cuvier, Diet. des. Sci. Nat., 6, p. 306 



(in part) ; substitute for amphibius. 

 1828. Arvicola aquatica Fleming, Hist. Brit. Animals, p. 23; the 



specific name adopted from Leach, Syst. Catal. Spec. Indig. 



Mamra. and Birds, Brit. Mus., 1816, p. 7 (where it is a nomen 



nudum). 

 1835. Arvicola amphibia Jenyns, Man. Brit. Vert. Animals, p. 33 



(in part). 

 1837. Arvicola amphibius Bell, Hist. Brit. Quadr., ed. 1, p. 321, and 



ed. 2, 1874, p. 316; Macgillivray, British Quadr., 1846, pp. 68 and 



260. 

 1842. Arvicola americana Gray, Ann. Mag. N.H., 10, p. 226; described 



from half -grown indi^dduals supposed to have been taken in South 



America; co-typos B.M., Nos. 42.4.12.6-7. 

 1845. Arvicola amphibius, sub-var. nigricans de Selys-Longchamps, 



Atti deUa sesta Riunione degli Scienziati Italiani, Milano, 1844, 



p. 322 ; pubhshed without description and hence a nomen midum. 

 1857. Arvicola amphibius a, Blasius, Saugethiere Deutschlands, p. 344. 



1895. Microtus amphibius Lydekker, Handbook to the British 

 Mammalia, p. 216. 



1896. Microtus {Arvicola) terrestris Miller, N. Amer. Fauna, No. 12, 

 pp. 66, 67 (in part). 



1910. Arvicola amphibius amphibius Miller, Proc. Biol. Soc. Washing- 

 ton, 23, p. 19; Catal. Mamm. W. Europe, 1912, p. 730; Barrett- 

 Hamilton, Hist. Brit. Mamm., 2, 1914, p. 482. 



1910. Arvicola terrestris amphibius Trouessart, Faune Mamm. d'Europe, 

 p. 194. 



