66 ANNALS OF SCOTTISH NATURAL HISTORY 



remained for the winter. In all we obtained eight specimens 

 of various ages. The average measurements of the four 

 largest are in excess of the average for mainland specimens, 

 and in colour they are rather more tawny, but the differences 

 are not sufficiently marked to allow them to be separated 

 from Mus musculus proper. 



We also found the Field-mouse very plentiful in the 

 crofts, but it was not confined to the cultivated ground like 

 the House-mouse, for we caught several examples among 

 the short heather on the higher parts of the island near the 

 north end. The natives say they kill numbers in their corn 

 stacks when thrashing during the winter. 



Out of the thirteen specimens brought home, six are 

 adult, and anyone acquainted with the ordinary Field-mouse 

 of the mainland is at once struck by their large size and 

 rich colouring. 



Before proceeding to a detailed description of these Fair 

 Isle mice, it may perhaps be as well to state briefly the 

 distinguishing characteristics of the various sub-species of 

 Field-mouse found in the British Isles. Captain Barrett- 

 Hamilton, in his paper 1 "On Mus sylvatiats and its Allies" 

 describes five sub-species as found in Great Britain. 2 These 

 are as follows : 



1. Mus sylvatiats intermedius, Bellamy. This is the ordinary 



form of Field-mouse found throughout the British Isles 

 (except where its place is taken by other forms) and parts 

 of the continent. 



2. Mus sylvaticus celticus, Barrett-Hamilton. A dark small- 



bodied Field-mouse, with a rather larger ear and foot, in 

 proportion to its size, than M. s. intermedius. Found in 

 the west of Ireland, Skye, the Outer Hebrides and, accord- 

 ing to Mr. J. G. Millais, :i in the north of Shetland. 



3. Mus sylvaticus hebridensis, De Winton. A larger and stouter 



built Field-mouse than M. s. intermedius, with proportion- 

 ately smaller ears, larger feet and shorter and thicker tail. 

 The colour of the upper side is hardly so bright as in 

 intermedius, and the under-side is "generally dusky or 



1 "P.Z.S." 1900, pp. 387-428. 



2 Mus sylvaliciis typicus, Linnreus, the type of this species is found in Norway, 

 Sweden, parts of Denmark, and perhaps the southern shores of the Baltic. 



3 " Mam. Great Britain and Ireland," ii. p. 185. 



