XVII. 

 The Common House-mouse. 



Mus musculus Linn. 

 (L. Mus, a mouse; L. musculus, diminutive of mus.) 



Mus musculus Linn., 1758, Syst. Nat. X ed., I, p. 62. 

 Type Locality. — Sweden. 



French Canadian, la Souris domestique. 



The Family Muridce, or Mice, are small rodents with more 

 or less naked tails covered with scaly skin, but not flattened 

 above; not more than 3 grinders in lower jaw. 



The genus Mus (Linnaeus, 1758) contains the Old- 

 World Mice and Rats, which are typical rodents, small in 

 size, with large ears, small eyes, tail nearly as long as the 

 body, naked or nearly so, tapering from base to tip, and covered 

 with scales more or less in rings; no cheek pouches. Colour, 

 dull black or grayish brown. But the teeth are the most 

 important feature of this group. 



The formula is: 



T 1-1 1 3-3 C 



Inc. ; mol. ^^-^=16 



i-i 3-3 



The upper molars have tubercles in series of 3 across the 

 crown of the tooth, instead of 2 in a series, as with the American 

 Mice. 



The pattern will be better understood by means of the 

 outlines in Fig. 140, which, however, are purely diagrammatic, 

 varying in details, not only with each species, but with each 

 individual and epoch in the life of that individual. 



The Common House-mouse has, in addition to the generic 

 characters, the following: 

 SIZE Length, 7 inches (178 mm.); tail, 3I inches (89 mm.); 



hind-foot, \\ inch (18 mm.); ear, \ inch long (13 mm.). 



The long, sharp nose also is a marked feature. 



480 



