ARVICOLA 403 



grizzled bistre on back and a greyish wood-brown on sides. 

 Cheeks and sides noticeably sprinkled with black-tipped hairs. 

 Under parts slaty grey, washed with pale ochraceous bufE on 

 chest and belly. Feet hair brown. Tail blackish above, greyish 

 below ; seldom distinctly bicoloured. 



For external and cranial dimensions, see tables at end of 

 volume. 



7. Arvicola terrestris Linnaeus. 

 (Synonymy under subspecies.) 



Range. — Widely distributed in Europe and Asia, its range 

 extending from Scandinavia eastwards at least as far as Lake 

 Baikal. Not found in the lowlands of west-central Europe, in the 

 Swiss Alps, Pyrenees, or Iberian Peninsula. Occurring in the 

 Italian Alps and Italy, and thence eastwards through Bosnia and 

 Rumania to the Caucasus, shores of the Caspian and Elburz 

 Mountains in N.W. Persia, whence it ranges probably continu- 

 ously across Central Asia to the neighbourhood of Lake Baikal. 



Characters. — Size, in European forms, somewhat smaller than 

 in A. atnphihius and A. sapidus, but Asiatic subspecies are more 

 nearly equal to the two species of Western Europe. Skull slightly 

 more modified for terrestrial and fossorial habits than in A. 

 amphihius and A. sapidus, but less specialized in this direction 

 than that of A. schennan. Auditory bullae of medium size or 

 small. Cheek-teeth moderately heavy and of normal pattern. 

 Colour variable according to the subspecies ; cheek-patches 

 reddish or yellowish and, in most forms, noticeably contrasted 

 with the surrounding parts. 



Geographical differentiation. — Eight more or less well-marked 

 subspecies of A. terrestris are now recognized, but of these three, 

 viz., A. t. ilUjricus, A. t. musignani and A. t. meridional is, are still 

 imperfectly known. All the forms are very closely related to each 

 other and the essential characters of the species as a whole shade off 

 through such forms as A. t. persicus and A. t. scythicus in the direc- 

 tion of A. amphihius and A. sapidus, and through A. t. terrestris 

 towards A . scherman ; indeed actual intergrading of A . scherman 

 and A. terrestris may be demonstrated to occur in the neighbour- 

 hood of the Baltic. The forms A. italicus, A. illyricus and A. 

 musignani are treated by Miller in his Catalogue as full species ; 

 but I can find no character in the existing material that will serve 

 to distinguish any one of them satisfactorily as a species distinct 

 from A. terrestris. The presence of such forms as A. t. scythicus, 

 A. t. persicus and A. t. rufescens in Asia and Asia Minor makes it 

 probable that the range of the species is quite continuous from 

 Scandinavia to Italy and the Southern Alps, although it has to 

 make a wide detoixr to pass round the great area of Central 

 Europe occupied by A. scherman. 



