mus 865 



Tail noticeably shorter than head and body 



(exceptions very rare) ; colour of underparts 



usually whitish in abrupt contrast with that 



of sides ; condylobasal length of skull rarely 



attaining 21 mm. ; hind foot usually 15 to 



17 mm. (Field mice, rarely entering houses)... M. spicilegus, p. 877. 



General colour above a clear rather dark greyish 



brown with no decided yellowish or russet 



tinge (eastern and east-central Europe, 



Sweden) M. ». spicilegus, p. 878. 



General colour above not clear greyish brown 

 unless very pale, the back usually with 

 decided yellowish or russet tints. 

 Colour of upper parts ranging from nearly 



clear buff to pale buffy grey (Spain) M. s. hispanicm, p. 879. 



Colour oE upper parts brownish grey, usually 



with a decided russet tinge (Portugal) ... M. s. lusitanieus, p. 882. 



MUS MUSCULUS Linmeus. 

 (Synonymy under subspecies.) 



Geographical distribution. — At present almost cosmopolitan ; 

 everywhere characteristically associated with human dwellings, 

 though not infrequently found at a distance from houses. 



Diagnosis. — Size medium (head and body about 75 to 100 mm., 

 hind foot, 17 to 19 ■ 4 mm., condylobasal length of skull, 19-8 to 

 22 • 4 mm.); tail about as long as head and body, often longer, 

 rarely much shorter ; hind foot narrow and slender, its greatest 

 width across base of toes about 3 to 3 ■ 5 mm. ; colour of under- 

 parts usually greyish buff, rarely forming any decided contrast 

 with the dusky brown or buffy brown of sides and back. 



External characters. — General form rather slender, with no 

 special peculiarities. Ear moderately large, extending a little 

 beyond eye when laid forward, its outline broadly oval ; a well 

 developed but low ridge on inner surface behind meatus ; entire 

 surface of ear finely pubescent except internally toward base. 

 Fore foot with thumb reduced to a small tubercle with very 

 rudimentary appressed nail ; fifth finger extending slightly 

 beyond base of fourth ; second nearly equal to third and fourth 

 which are sub-equal and longest ; tubercles small, occupying 

 distinctly less than half the surface of palm ; the three anterior 

 are nearly circular in outline and about as large as thumb, that 

 lying at base of fifth finger with small but distinct supplemental 

 outer tubercle, the two posterior are decidedly larger and some- 

 what elongated ; surface of palm between tubercles irregularly 

 tuberculo-reticulate ; scales on under surface of fingers tending 

 to be divided at middle. Hind foot relatively shorter and more 

 robust than in Apodemus sylvaticus, its greatest width at base of 

 toes about 3 to 3 • 5 mm. ; the three median toes sub- equal, the 

 inner usually not so long as the others ; first digit extending 

 about to base of second, fifth extending a little beyond base of 

 fourth ; sole naked except at sides of heel, its surface smooth 



3 K 



