648 MURIDiE— MUS 



of the North African element in the Portuguese fauna." In the 

 eastern Mediterranean region M. gentilis, Brants, and in southern Asia, 

 M. bactrianus, Blyth, apparently represent the same group of wild, light- 

 bellied House Mice. 



It cannot be said that our knowledge of the status of the forms 

 mentioned above is in a very satisfactory state. The characters by 

 which these forms are distinguished from M. musculus are for the most 

 part of trivial importance, and hardly sufficient to raise these mice 

 above the rank of sub-species of musculus. The forms in question, 

 however, seem to have found their way to Europe at very different 

 times, by different routes, and in different ways ; some, like spicilegus, 

 have spread westwards and northwards naturally, while others, like 

 musculus, have travelled as the constant companions of man. More- 

 over, it is just possible, as noticed above, that the genus was present 

 here during part of the Pleistocene ; and if this be so, either M. muralis, 

 fcsroensis, or spicilegus, or all three, may be the descendants of this 

 ancient stock. For the present, therefore, pending further research 

 upon the very difficult problems involved, it would seem better to 

 follow the somewhat delicate classification adopted by Miller, than to 

 group all these forms as mere sub-species of musculus. 



A systematic study of the American colonies of Mus and Epimys 

 might yield important information concerning the mechanics of 

 geographical variation. The absence of native Murincz from the New 

 World eliminates one of the chief difficulties attending such research in 

 the Old World ; for, in the latter, we cannot ascertain to what extent 

 newcomers have blended with indigenous species of these genera in 

 any given region. J. A. Allen {Bull. Am.' Mus. Nat. Hist., 1894, 175; 

 1895, 236; 1896, 59; 1897, 35, 116, 198 (Allen and Chapman); 1899, 8; 

 I903) 540; 1904, 435 ; and 1910, loi) has given detailed descriptions of 

 many American specimens of Mus. House Mice from Cajabamba, 

 Peru, showed a strong tinge of rusty buff, and similarly coloured 

 examples are before us from Ecuador and Cordoba, Argentina ; those 

 from Santa Marta, Colombia, were also rather more fulvous above and 

 below than are normal specimens from the United States ; those from 

 San Jos6, Costa Rica, were unusually pallid. In Texas and Arizona 

 the species lives, in many places, a quite wild life, and is developing a 

 remarkably red coloration. House Mice were found at Jalapa, Vera 

 Cruz, inhabiting "old fields" in company with native rodents; these 

 mice have been recognised by Allen and Chapman as forming a distinct 

 sub-species, their M. musculus jalapcz, characterised by having the mid- 

 dorsal region and tail of a uniform deep black throughout, the sides 

 yellowish-grey, or ordinary mouse colour, the belly pale buffy grey, 

 and the feet and ears dark brown. Similarly, dark coloured mice, 

 perhaps belonging to the same sub-species, occur in Nicaragua. Winge 



