444 MURID^— AGRESTIS 



History: — Although described by Bellamy in 1839, it cannot be 

 pretended that the status and affinities of this mouse have been made 

 at all clear until quite recently. All the earlier descriptions, even when 

 technically valid, must be regarded as due to misapprehensions, the 

 earlier writers not having been acquainted with the true relationships 

 of agrestis and the continental arvalis. 



The exact distribution of this Grass Mouse is imperfectly known, 

 but it certainly ranges from Wales to Austrian Galicia, ascending to 

 4000 feet in Switzerland (Fatio). The common European form, which 

 is found from the eastern shores of the English Channel and the Baltic 

 at least to Central Germany and South-western France, is just dis- 

 tinguishable as a sub-species, M. h. bailloni (de S^lys), on account of 

 its narrower skull. Another sub-species, M. rozianus (Bocage) of 

 Portugal and North-western Spain, which differs chiefly in its small 

 auditory bullae, is graded as a sub-species oi agrestis by Miller, but may 

 prove to be more nearly related to hirtus. 



M. hirtus is the Grass Mouse of England, Wales, and the lowlands 

 of Scotland, where it is common all over the country, including the 

 islands of Wight and Anglesey, except in woods and on the higher 

 hills. In the Highlands of Scotland and probably on the hills of the 

 south, also in the Hebrides, it is replaced by one or other of the forms 

 of M. agrestis, and in the Orkneys by M. orcadensis. It is absent from 

 Ireland, the Isle of Man, Bardsey Island, and, as far as is known, from 

 all other islands except those mentioned above. 



Distribution in time and Status : — This mouse is not known as a 

 fossil in Britain, although remains of "voles" are numerous in late 

 pleistocene deposits. It is therefore probably a quite recent post- 

 pleistocene immigrant, which appears to have established itself in the 

 more low-lying and southern parts of the country, at the expense of 

 the older forms of the M. agrestis type, in a manner paralleled by that 

 oi Lepus europceus zx\A Evotoniys glareolus. It appears to have arrived 

 in Britain before the separation of Wight and Anglesey, but after that 

 of all the other islands. 



Description: — The Common Grass Mouse is distinguishable in its 

 genus by its comparatively small size (hind foot, 17 to 18, and condylo- 

 basal length of skull not more than 24-6 to 26 mm.), small bullae, and 

 comparatively reddish upper side. 



The colour of the upper side is near " tawny russet," very indistinctly 

 overlaid with black. The sides are paler and washed with buff; the 

 under-side and feet are light ochraceous buff, through which colour the 

 dusky basal portions of the hairs show here and there. The tail is 

 bicoloured, above brown, beneath like the belly. 



The brightest individuals run very near Evotomys glareolus, but lack 

 the clear light belly of the latter. 



