MICE AND RATS. l8l 



]\Iice and Rats, and the second the Voles. In Britain each 

 section is represented by a single genus only, although there 

 are several other foreign genera in both. 



In habits the majority of the British forms are mainly terres- 

 trial, although one species is aquatic, and all are able to climb 

 with more or less facility. 



THE MICE AND RATS. GENUS MUS. 

 ATus^ Linn., Syst. Nat. ed. 12, vol. i. p. 79 (1766). 



Molar teeth furnished with roots and surmounted by tuber- 

 cles \ the latter forming three longitudinal rows in the teeth of 

 the upper jaw ; incisors narrow, and devoid of grooves on their 

 front surfaces. Eyes and ears large ; extremity of muzzle 

 naked ; first rudimentary toe of fore-foot with a short nail in 

 place of a claw ; tail long, tapering, and nearly naked, with 

 overlapping scales arranged in rings ; fur soft, and (in British 

 species) without an intermixture of spines. 



Light and active in their movements, and bright-eyed in 

 appearance, the Mice and Rats, in addition to the distinctive 

 character of their molar teeth, are specially distinguished from 

 their British allies by their pointed muzzles, long scaly tails, and 

 large ears. Purely terrestrial in their habits, they generally fre- 

 quent houses, farm-buildings, stables, and corn-ricks, rather 

 than the open fields, although the Harvest-Mouse is to a certain 

 extent an exception to this rule. 



The genus includes a larger number of species than any 

 other in the whole Mammalian class, and, with the remarkable 

 exception of Madagascar, is distributed over the whole of the 

 Old World. Its head-quarters aie, however, the Tropical Re- 

 gions of that Hemisphere, whence there is a gradual diminution 

 in the num')er of species, as we proceed north and south, till, in 

 the Sub-Arctic region, they become very few. 



