52 



Rats and Mice 



The Microtinae, or Voles and Lemmings, had many species 

 and genera Hving in Pleistocene Britain. Most of these forms are 

 now quite extinct here, although certain of them are still repre- 

 sented in continental Europe, or by more or less modified 

 descendants which linger on various small islands around our 

 coasts, as in the Orkneys and Hebrides. One of the most 

 astonishing features in the distribution of this sub-family is the 

 fact that, although remains of Lemmings occur in great abundance 

 in the Pleistocene cavern deposits of Ireland, there is apparently 

 no trace at all of either fossil or living Voles in that country. 



In Great Britain itself three or four species of Vole are now 

 living. These may be distinguished as follows : — 



A. Cheek-teeth (Fig. 4 B) each with two well-developed roots or 



fangs in adults. Lower molars with their triangles peculiarly 

 rounded, and not completely shut off from each other. 



Size small (hind-foot 15*4 to 17*4 mm.*; condylo-basal 

 length of skull 21 to 24 mm.). Tail densely haired, half as long 

 as head and body. Ears conspicuous above the fur. 



Bank Vole, Evotomys glareolus. (Distributed through- 

 out the country.) 



B. Cheek-teeth (Fig. 4 C and D) persistently growing and never 



developing roots. Triangles not rounded off, and from three to 

 five of them are completely shut off from each other in the 

 front lower molar. Ears not conspicuously projecting from 

 the fur. 



a. Size small (** Field Mice "). Tails about one-third the 

 length of head and body, less densely haired than in Evotomys. 

 Anterior lower molar with five closed triangles (Fig. 4 D). 



1. Size relatively small (hind-foot 17 to 18 mm.). General 

 colour tawny russet. 



Short-Tailed Field Vole, Microtus hirtus. (Distributed 

 throughout England and the Lowlands of Scotland.) 



2. Size slightly larger (hind-foot 18 to 19 mm.). General 

 colour darker and browner. 



Highland Field Vole, Microtus agrestis 7ieglectus. 

 (Distributed in the Highlands of Scotland.) 



6. Size large (" Water Eats "). Heavily built. Tail about 

 half the length of the head and body, its hairs nearly con- 



* 25 millimetres = 1 inch. 



