432 MURIDA:—AGRESTIS 
M. hirtus is sufficient to account for the present restriction of the older 
agrestis to islands, mountains, and northern regions, where the com- 
petition is only moderately severe. In addition, the larger and 
extremely palatable forms of MWzcrotus probably find a difficulty, like 
the lemmings, in escaping from their enemies in the absence of 
moderately heavy snow. They thus survive only where carnivora 
are scarce, or where the coarse herbage both feeds and protects 
them. This coarse herbage has no attractions for the newer dominant 
species, which prefer the richer diet more easily obtainable in warmer 
or more cultivated districts. 
The British sub-species are as follows :— 
MACGILLIVRAY’S GRASS MOUSE. 
MICROTUS AGRESTIS MACGILLIVRATI, Barrett-Hamilton and Hinton. 
1913. MICROTUS AGRESTIS MACGILLIVRAII, G. E. H. Barrett-Hamilton and M. A. C. 
Hinton, Adstract Proc. Zool. Soc. London, No. 119, 15th April, 18, and Proc. 
Zool. Soc., London, 1913, 831; described from Islay, Scotland; type specimen, 
No. 14.1.30.1 of British Museum collection. 
Distribution and History :—This Grass Mouse appears to be con- 
fined to Islay, where the existence of a “ vole” seems to have been first 
reported by T. F. Gilmour, who sent one found dead on 30th July 1905 
to the editors of the Aun. Scott. Nat. Hzst. (1905, 242). An immature 
specimen from Kildalton, too young for determination, was submitted by 
Kinnear to Miller (Axx. and Mag. Nat. Hist, February 1908, 201); and 
three young found in a rick were forwarded to Thomas by Russell 
(Zoologist, 1910, 115), who did not think the animal common. A series 
of fourteen caught by Sheppard in the woods around Bridgend at once 
showed the distinctness of this mouse, which might well be called a 
species were it not that the sub-specific name indicates its relation- 
ships. Sheppard visited the island twice, and reported after his first 
visit that the animal was very scarce, as he was only successful in find- 
ing two colonies—one in a small belt of hazel, known as Dale Bush, the 
other in a walled graveyard about two miles south of Port Ellen, on 
the border of the district known as the Oa. On his second visit he 
found grass mice, shréws, and field mice all using the same runs in 
open ground overgrown with brambles, raspberries, and coarse grass. 
Description :—MacGillivray’s Grass Mouse resembles the more 
widely distributed JZ. a. evsu/ (next to be described) in size and general 
proportions, but may be recognised at all seasons by its much thinner 
coat (length of dorsal hairs reaching about 8 mm.) and duller coloration, 
especially on the under-side. The skull also shows some peculiar 
characters, as described below. 
Colour :—The upper side is rich “ buff,” of a slightly duller tint than 
