THE HEBRIDEAN FIELD MOUSE 533 
the specimens from Callernish and Tarbet, Harris, there is in eastern 
Lewis a well-marked deviation from the typical form of Uig. Barrett- 
Hamilton (Proc. Zool. Soc., London, 1900, 401) referred three small 
dark specimens from Eisken, eastern Lewis, to his J7. sylvaticus celticus, 
and he mentions (af. cz¢., 395, 403) that de Winton thought that this 
small form might be an accidental introduction, his hedridens’s keeping 
to its own side of the island. The Eisken specimens may have been 
immature. A series of fourteen adults and two young specimens were 
collected at Stornoway by Mr D. Anderson in the latter part of March 
1913. Apart from the uniform reduction of size which they show when 
compared with the typical series from Uig, there is little in external 
appearance to distinguish thése specimens from true hedridensis. Some 
of the males are silvery below, like those from Callernish, but in others 
and in the females there is a more or less well-marked tendency for 
the lower parts to be suffused with buff. In a young male (head and 
body, 77) the coat is like that of the adult, having the flanks lighter 
than the back, the under-surface silvery, with a bright pectoral spot 
and a paler median wash of buff behind; in a young female (head and 
body, 78) the flanks are still dark, and though a faint trace of the buff 
stripe can be seen, the under-surface is greatly darkened by the bases 
of the hairs (cf p. 532). In average size the skulls are slightly 
smaller than in typical “ebridenszs (condylo-basal length, 23-64 instead 
of 24-1 mm.); they are relatively broader and the post-molar length is 
very slightly increased, the palatal length still more slightly diminished; 
but in both the latter respects there is substantial agreement with 
hebridensis and considerable difference from any British form of 
sylvaticus, These specimens may eventually have to be separated from 
h. hebridensis, but the separation cannot be made until a much more 
extensive series of skulls from western Lewis than that at present 
available has been acquired. 
In the few specimens available at present from Barra the backs are 
brighter than in 4. hebridenszs, there being fewer black hairs; the under- 
surface is silvery, with scarcely a trace of a pectoral spot or buffy 
suffusion ; the line of demarcation is clearly defined. In the single 
adult skull the small size (condylo-basal length, 23-1) and greater breadths 
are nearer to the Stornoway series than to typical Zebrzdenszs ; a marked 
feature is that the palatal length is shorter than in any other form 
of hebridensis, though, on the other hand, such short palates occur 
occasionally in individuals of the other races. 
Two specimens from South Uist resemble those from Barra in the 
slight development of a ventral buffy suffusion ; although old, the small 
size, in particular of the feet, is noteworthy. 
Mention may be made here of two field mice taken on Bigg, 29th 
March 1913, by Mr P. D. Montague. Like the grass mouse of the 
