434 MURIDA—AGRESTIS 
Status :—This mouse, like the shrew and stoat of the island, is 
peculiar to Islay, which has evidently long been separated from the other 
islands and the mainland of Scotland. MacGillivray’s Grass Mouse is 
slightly more primitive in pelage and skull than the other forms of J/. 
agrestis, and so may be regarded as an insular survival rather than as a 
new development. 
THE HEBRIDEAN GRASS MOUSE. 
MICROTUS AGRESTIS EXSUL, Miller. 
1908. MICROTUS AGRESTIS EXSUL, G. S. Miller, Amn. and Mag. Nat. Hist. 
February, 201; described from North Uist, Outer Hebrides; type specimen, 
No. 6.3.1.3 of British Museum collection ; Trouessart ; Miller (Catalogue). 
1909. MICROTUS AGRESTIS INSUL, R. Lydekker, Zool. Record, 1908, xlv., Mamm., 
74; accidental renaming of exsw/. 
History :—The occurrence of Grass Mice in the Inner Hebrides has 
long been known, but, with those of Orkney and the mainland, they 
have generally been lumped together as representing one widely dis- 
tributed species. From South Uist they were first reported to Harvie- 
Brown by M‘Donald of Rodil and Henderson of Loch Boisdale, 
and in 1879 Harvie-Brown himself captured a specimen at Newton, 
North Uist. The relationships of the Outer Hebridean form were, 
however, not recognised until Miller began his work for his Catalogue ; 
his description of evsw/ was based on fourteen examples from North and 
South Uist, all of which except three had been taken by Kinnear, who 
supplied the first properly prepared specimens of this form. The 
presence of “voles” on other Scottish islands was also long known, 
having been mentioned by Alston in 1880; but, in the absence of 
systematic collecting, they could not be submitted to accurate study 
until the receipt of Sheppard’s specimens in 1912. (See footnote on 
Pp. 422 supra.) 
Distribution :—This is the Grass Mouse of the Hebrides generally, 
where it has thus far been found, often in abundance, on Arran 
(common, Alston), Gigha, Jura, Mull, Skye, North and South Uist, and 
Benbecula. In Jura it is sometimes so numerous as to be a danger 
to young plantations (Henry Evans, zz Zt. 11th February 1900). It 
probably occurs also in other islands, as Rum (Millais). It is absent 
from Lewis (Duns, 1865, 620, and later writers), but there are distinct 
forms in Islay, Eigg, Muck, and Bute. 
Description :—This large Grass Mouse differs from the Skandinavian 
M. a. agrestis only in the frequent presence of a small posterior fourth 
inner angle in m1. From the Common Grass Mouse it may be 
distinguished by its much larger size and duller brown colour. From 
M, a. macgillivrai it differs in its slightly brighter colour, thicker pelage, 
and in the skull characters as already described above on p. 433. 
