428 MURIDA:—AGRESTIS 
c 
inner fold (counting from behind) fails to meet the third outer ; 
or the anterior loop is complicated by the development of one 
or more additional salient angles and infolds on either side 
anteriorly. 
The British species and sub-species are as given below. 
They fall into two groups :— 
1. Agrestis group. 
(1) WW. agrestis macgilivrait, of Islay. 
(2) I. agrestis exsul, of the Outer and Inner Hebrides. 
(3) WZ. agrestis mal, of Eigg. 
(4) WW. agrestis neglectus, of the Scottish Highlands. 
(5) JZ. agrestis luch, of Muck. 
(6) W. hertus hirtus, of Britain south of the Highlands. 
2. Orcadensts group. 
(7) A. orcadensis ronaldshaiensis, of South Ronaldshay. 
(8) J. orcadensis orcadensis, of Pomona. 
(9) JZ. orcadensis rousatensts, of Rousay. 
(10) IZ. orcadensis westre, of Westray. 
(11) MW. orcadensis sandayensis, of Sanday. 
Much new material has been received only since the publi- 
cation of the earlier pages on AZzcrotzne, and therefore two 
sub-species of agrestis—mial and luch—and two of orcadensis— 
ronaldsharensts and vousatensis—could not be included in the 
Key to the Wuside on pp. 377-381. 
Group AGRESTIS. 
Miller grades all the west European Grass Mice having an 
extra prism in ° as sub-species of agrestzs. This method, 
however, obscures their relationships, especially the fact that, 
as in Evolomys, a newer, smaller form, JZ. £:rtus, has replaced 
an older, larger, JZ. agrestis, the latter now confined chiefly 
to northern regions, and with isolated southern colonies on 
mountains. These two forms are of entirely distinct origin, 
and are here given specific rank, and each has sub-species. 
Like Lepus timtdus, Evotomys skomerensts, alstoni, and erica, 
M. agrestis belongs to an older fauna; AZ. hertus to that of 
Lepus (Eulagos) europeus and Evotomys glareotus. 
