THE MOUSE TRIBE. 131 



litter is produced early in the spring, a second one follows during the summer. 

 When their holes are rendered inaccessible by frost, water- voles are found to take 

 shelter on shore, sometimes frequenting the cover afforded by an osier-bed, and on 

 other occasions taking refuge in pollard willows. In spite of its feet not being 

 webbed, the water-vole is an expert swimmer and diver ; and its coat is of such a 

 nature as to throw off the water as readily as dues tin' plumage of a duck. Fossil 

 remains of the water-vole are found in the cavern -deposits of England, and 

 also in the "forest-bed" of the Norfolk coast; while those of extinct species of the 

 genus to which it belongs, occur in the Pliocene crag-deposits of Suffolk and Essex. 

 Short-Tailed In addition to the water-vole, the British Islands (exclusive of 



Field voles. Ireland) possess two other species of the same genus, the commonest 

 of which is the short-tailed field-vole, or field-mouse (.V. agrestis). This species is 



- - i 



THE CONTINENTAL FIELD-VOLE ( Dat size). 



.vV^VWO 



about the size of an ordinary mouse, and is greyish brown in colour above, and 

 greyish white beneath, with dusky feet : the tail being about one-third the length 

 of the body, while the under surfaces of the hind-feet have six naked pads. It is 

 specially characterised by the circumstance that the second molar tooth in the 

 upper jaw has five prisms. This character, unimportant as it may seem, serves to 

 distinguish this species from the continental field-vole (M. arvalis) — represented in 

 the accompanying illustration — in which, in common with the other continental 

 short-tailed members of the genus, the corresponding tooth has but four 

 such prisms. 



The common short-tailed field-vole is found all over England and Scotland, as 

 well as the greater part of the Continent ; its range extending from the north of 

 Italy to Finland, and from Spain and France to Russia ; but in the southern 

 portion of its habitat it is less numerous than the continental field-vole. The 

 English species is commonly found in meadows — especially those where the ground 

 is moist, and makes extensive runs beneath the grass, in which it roams both by 



