8(14 



lending to disappear, in some species without trace of first 

 lamina ; upper incisor compressed, set at such an angle that a 



a b 



Fig. 17(i. 

 Upper incisors uf Kjiimi/* (n) and J/". 1 - (b). 

 Mniii enlarged. 



sub-apical notch is normally cut in its outer side by action of 

 lower tooth. 



Ileum ds. -The genus Mux as now restricted contains the 

 J/»s uiHxriiltw group and the Asiatic and African species usually 

 referred to Lcggada. Though the species differ considerably 

 among themselves in details of structure the group is very 

 homogeneous as regards the peculiar specialization of the 

 mechanics of the molars and the distortion of the first lamina 

 of m 1 - About twenty-five forms are now known, seven of which 

 occur in Europe. 



KEY TO THE EUROPEAN FORMS OP MDS. 



Hind foot broad and robust, its width at base of 

 outer toes 4 to 5 mm. 

 Condylobasal length of skull in adults 21-6 to 

 22-2 mm.; hind foot 17-4 to 18-8 mm. 



(St. Kilda Island, Scotland) M, muralis, p 874. 



Condylobasal length of skull in adults 23 to 



23-4 mm; hindfoot 19 to 20 mm. (Faeroes)... 31. fmroensis, p. 875. 

 Hind foot narrow and slender, its width at base of 

 outer toes about 3 mm. 

 Tail about as long as head and body, often longer, 

 rarely much shorter ; colour of underparts 

 usually greyish, rarely contrasted with that 

 of sides ; condylobasal length of skull fre- 

 quently more than 21 mm. ; hind foot usually 



17 to 19 mm. (House mice) M. musculus, p. 865. 



General colour dark and brownish, usually 

 without evident yellowish tinge, the belly 

 dusky greyish (central and northern 



Europe) a M. m. musculus, p. 869. 



General colour light, usually with a decided 

 yellowish tinge, the belly buffy greyish 

 (Mediterranean region) if. ■»,, azm-icus, p. 871. 



