LOCALLY EXTINCT VOLES 467 



LOCALLY EXTINCT VOLES. 



Microtus arvalis (Pallas, Nov. Sp. Quadr. e. Glir. Ord., 78, 

 1778) differs from M. agrestis in its smaller size; broader, 

 shorter, more depressed, and less angular brain-case ; and in it^ 

 having only two instead of three salient angles on the inner 

 side. Miller recognises four sub-species in western and central 

 Europe, viz., M. arvalis arvalis, Pallas, known from Germany, 

 Belgium, France, Switzerland, Austria- Hungary and northern 

 Italy, characterised by its small size (hind foot, 15 to 17 mm. ; 

 condylo-basal length, 23 to 25 mm.) and normal skull; M. a. 

 merzdianus (Miller, Ann. and Mag. Nat. Hist., February 1908, 

 197) from south-western France (Pyrenees), a slightly larger, 

 more yellowish form (hind foot, 15.8 to 16.6 mm. ; condylo-basal 

 length about 25 mm.); M. a. duplicatus (Rorig and Borner, 

 Arb. aus d. Kais. Biol. Anstalt f. Land- u. Forsttvirthschaft, 

 v.. Heft ii., 73, 1905), from the Baltic coast of north-eastern 

 Germany, a large pallid form with robust skull and deep brain- 

 case (hind foot, 17 to 18.6 mm.; condylo-basal length, 25 to 

 25.5 mm.), and M. a. levis (Miller, Ann. and Mag. Nat. Hist., 

 February 1908, 197) from Rumania, southern Hungary, and 

 north-eastern Italy, resembling duplicatus in its large size and 

 pale coloration, but with the skull slender, the brain-case long, 

 narrow, and smoothly rounded, and usually with relatively 

 large auditory bullae. Other nearly related forms carry the 

 range of the species far to the east through Siberia and 

 central Asia. 



On several occasions fossils from various British deposits 

 of late Pliocene and Pleistocene age have been determined as 

 belonging to M. arvalis {e.g., from fissures near Bath, Somerset, 

 by Blackmore and Alston, Proc. ZooL Soc, 1874, 468) ; but in 

 most cases such records imply, because of the fragmentary 

 nature of the material on which they are based, nothing more 

 than the presence of a "vole" with an arvaloid, i.e. a normal 

 dentition. Some rather well-preserved cranial fragments have 

 been collected from the late Pleistocene of Ightham by Abbott, 

 Corner, and others, and Hinton [Proc. Geol. Assoc, xxi., 495) 

 finds that these are " apparently identical " with M. a. arvalis. 



