520 MURID^— APODEMUS 



species, distinctly greater zygomatic, inter-orbital, and cranial breadths, 

 a deeper brain-case, shorter post-molar region (the bullae being, however, 

 enlarged rather than diminished), longer and rather wider nasals, 

 greater palatal length, slightly longer and much wider incisive foramina, 

 narrower rostrum, and longer molars. 



For external and cranial dimensions, see tables at pp. 516 

 and 518 respectively. 



Status: — A. s. butei\% quite clearly differentiated from the English 

 A. s. sylvaticus, and may be regarded as an insular development of either 

 the same stock, or else of an older stock of mice of the sylvaticus type. 

 Its exact significance cannot be appreciated until the relationship of the 

 Highland Field Mice to those of England and the lowlands has been 

 determined. The Field Mice of Skye and the Highlands approach 

 A. s. butei more or less closely in some respects, and thus appear to 

 occupy an intermediate position between it and the English sylvaticus. 

 Among other Hebridean Field Mice the Bute form is readily dis- 

 tinguishable by its small size, dark coloration, and skull characters. 



The habits of the Field Mouse are not far removed from 

 being typical of those of mice generally. It is a hardy, active, 

 non-hibernating animal of primarily vegetarian, but, when 

 necessity arises, omnivorous diet, a fine jumper, a good climber, 

 a capable digger, and a fair svi^immer. It may, therefore, be 

 found in any situation frequented by mice, as it is not tied 

 down to the habitats of those which have become specialised 

 in any particular direction. Thus it cannot compete with the 

 House Mouse in the dwellings of mankind, and does not usually 

 accompany it or the Harvest Mouse to the stackyards. Its 

 activity and preference for a diet of berries and grain rather 

 than of grass, raises it above the monotony of a Grass Mouse's 

 existence, and keeps it in woods and the hedgerows of 

 cultivated lands ; it sometimes swarms in cornfields towards 

 harvest-time. But it is found also in more open and barren 

 districts, and is often numerous and well grown on desolate 

 islands or rough mountains. In Clare Island, Co. Mayo, 

 Ireland, it inhabits the walls of loose stones right up to the 

 summits of the hills, and in the opposite direction, it may be 

 found on the sea beach,^ generally- in the marram-grass,^ the 



' G. T. Rope, Zoologist., 1874, 3865. 



2 G. T. Rope {Zoologist, 1887, 206) thus encountered it between Dunwich and 

 Sizewell, Suffolk, on a beach cut off from cultivated land by wide marshes. 



