
438 MURIDA2—AGRESTIS 
THE EIGG GRASS MOUSE: 
MICROTUS AGRESTIS MIAL,! Barrett-Hamilton and Hinton. 
1913. MICROTUS AGRESTIS MIAL, G. E. H. Barrett-Hamilton and M. A. C. Hinton, 
Ann, and Mag. Nat. Hist., October 1913, 364; described from Eigg, Scotland ; 
type specimen, No. 14.1.30.3 of British Museum collection. 
Distribution and History :—This mouse is at present only known 
from the island of Eigg, where it was first taken by Montague in March 
and April, and by Anderson in June 1913 (see footnote on p. 422 supra). 
Millais had previously suspected the occurrence of Grass Mice on Eigg. 
Description :—J/. a. mial agrees generally in size and proportions 
with JZ. a. exsu/, but differs strikingly in pelage. The fur is longer and 
rather coarser in texture, so that the animal has a shaggy instead of a 
sleek appearance. This is due in great measure to the abundance 
and length of the long dusky hairs, which tend to darken the rump 
and flanks, leaving the general colour of the back very much as in 
exsul, The under-sides and the posterior surfaces of the hind legs are 
silvery in sharp contrast with the dark brown flanks; rarely the under- 
side shows faint traces of a median stripe of yellowish wash. 
The skull differs from that of ersw/ of equal age in having the 
nasals and basioccipital relatively a little shorter, and the auditory 
bullae slightly smaller. 
The teeth are as in evsw/. Amongst nineteen specimens, the fourth 
inner angle of 7! was entirely absent in only one; in three it was 
represented merely by a microscopic vestige; in eleven it was small 
but quite distinct ; and in four it was large and of regular form. 
Dimensions in millimetres:—head and body (young to middle- 
aged), 98 to 116; tail, 27 to 39; hind foot, 17 to 20; ear, 10 to 13. ‘In 
the type these items are respectively 113—-36—20—12. 
Skull :—Condylo-basal length of type (middle-aged), 27-4 ; breadth: 
zygomatic, 15-7; inter-orbital, 3-5 ; mastoid, 11-8; occipital depth, 6-3 ; 
length of nasals, 7-2; of diastema, 7-8; of maxillary tooth-row, 6-4; of 
mandible, 17-9; of mandibular tooth-row, 6:3. 
Status:—This mouse, as is shown most clearly by its dental and 
cranial characters, has its nearest ally in JZ. a. exvsul. It may be 
regarded as a peripheral and local development of the latter, which 
has arisen probably as a result of segregation for a long time upon a 
small island. 
Habits:—Montague found this mouse common amongst coarse 
heather ; it is not strictly nocturnal. 
1 Mial in Scotch Gaelic is the general word for beast. 
