THE RATS AND MICE 1311 



Quetta vole (E. fusricapillus] is about five inches in total length, of which half an inch 

 is occupied by the tail. It is brownish white above, with the exception of the grayish- 

 brown head, while the under parts, feet, and tail are white; the fur being long and 

 soft. -It is reported to construct horizontal galleries in the ground, with heaps of 

 earth thrown up at intervals, after the fashion of the mole. 



THE RATS AND MICE 

 Genus Mus 



The true rats and mice, together with certain allied forms referred to distinct 

 genera, are the representatives of the last subfamily of the Muridce, which is ex- 

 clusively confined to the Old World. They are primarily characteri/.ed by the 

 crowns of the unworn upper molar teeth carrying a number of tubercles arranged in 

 three longitudinal rows; these teeth always having distinct roots. When worn by 

 use, the crowns of the molars exhibit transverse bands of enamel. The tail is 

 always long and scaly, and in most cases almost destitute of hair. Moreover, the 

 ears are large, and the eyes bright and prominent, while the muzzle is sharply 

 pointed, and the build light and elegant. Their movements are quick, active, and 

 graceful, and their coloration is in most cases uniform and sombre, as would 

 naturally be expected from the nocturnal and burrowing habits of the majority of 

 the species. 



The Murine subfamily includes a considerable number of species, by far the 

 greater majority of which are comprised in the genus Mus. That genus is character- 

 ized by the incisor teeth being smooth, and the molars distinctly tuberculated. The 

 ears and eyes are proportionately large, and the tip of the muzzle is naked, while the 

 tail is long and scaly. The first toe of the fore-foot has a short nail in lieu of a- 

 claw, and the fur is soft, although in some cases intermingled with spines. The 

 genus is the largest in the whole Mammalian class, comprising not far short of a 

 hundred and fifty species, which are distributed over the whole of the Old World 

 with the exception of Madagascar; some of these, by human aid, having now 

 acquired a cosmopolitan range. With such a multitude of species, it is of course 

 only possible to allude to a few of the more interesting. 



The brown or, as it is often inappropriately called, the Norway rat 

 (M. decumanus}, offers one of the most remarkable instances of a suc- 

 cessful usurpation to be found in the animal kingdom; this creature having ousted 

 the black rat from most parts of England and a large area on the Continent. So far 

 as can be ascertained, its original home appears to have been Western China, from 

 whence it gradually traveled westward to continental Europe, finally reaching the 

 shores of the British Islands by the involuntary aid of ships. Its westerly migration 

 was, however, by no means limited to Europe, as it has been carried by vessels 

 across the Atlantic, and is now as abundant in many parts of North America as it is 

 in the Old World. The migration of the rat into Russia is known to have taken 

 place about 1727, in which year large troops of these animals crossed the Volga 



