226 MICROTIN^ 



E. kcnnardi is a most interesting and well-marked species, 

 belonging to the nageri group. It (or closely allied forms, with 

 large skulls and heavy cheek-teeth) occurs abundantly in the later 

 Pleistocene deposits of Britain and Western Europe in situations 

 which show that the nageri group, although now restricted to the 

 mountains and islands of Western and Central Europe, was 

 formerly widely distributed in the plains. The group thus 

 affords a parallel to the analogous cases of the Variable Hares and 

 Snow Voles, and its present restricted and peculiar distribution 

 is susceptible to a precisely similar explanation. The nageri 

 group is most probably to be regarded as the older and once 

 generally distributed representative of its genus in Western and 

 Central Europe. In late Pleistocene times, however, species of 

 the glareohis group invaded the region, arriving probably with 

 Microtus arvalis (of modern type) and other voles, and success- 

 fully competing with the older group gradually dispossessed the 

 latter of its foothold in the plains; so that to-day the older 

 group survives only in the security of mountain fastnesses and 

 insular seclusion. 



5. Evotomys nageri Schinz. 

 (Synonymy under subspecies.) 



Range.- — Mountainous regions of Western and Central Europe, 

 including Western Norway, the French side of the Pyrenees, the 

 Alps and the mountains of Italy southwards to Calabria. Allied 

 species occur in the late Pleistocene of Britain and are found living 

 in the Hebrides, on Skomer, and in the Channel Islands. 



Characters.- — Distinguished from E. glareolus, the lowland 

 species of the region, by its larger size; hind-foot (17-21 mm.) 

 usually 18 mm. or more ; condylo-basal length of skull, in adults 

 with well-developed molar roots, usually exceeding 24 mm. 

 (23-6-26). General colour darker and greyer, less brightly 

 rufous than usual in E. glareohis. Skull larger, more strongly built, 

 longer and narrower throughout, with moderately well-developed 

 post-orbital squamosal crests, and long and narrow mesopterygoid 

 fossa. 



Geographical differentiation. — Six subspecies are recognized, 

 namely, 



5a. Evotomys nageri nageri Schinz. 



1845. Hypudceus nageri Schinz, S_ynops. Mamm., 2, p. 237. 



1852. Myodes nageri Gerbe, Rev. et Mag. Zool., p. 449. 



1857. Arvicola glareolus b. Blasius, Saugethiere Deutschlands, p. 337. 



1862. Myodes bicolor Fatio, Rev. et Mag. de Zool., [2], 14, p. 257; 



described from Genthal, Berne, Switzerland; type in Geneva 



Museum. 

 1869. Hypudceus glareolus Fatio, Faune Vert, de la Suisse., 1, p. 221. 

 1900. Evotomys nageri Miller, Proc. Washington Acad. Sci., 2, p. 94; 



Trouessart, Faune Mamm. d' Europe, 1910, p. 167. 



