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 M. sylvaticus celticus, 

 and he mentions {pp. cit, 395, 403) that de Winton thought that this 

 small form might be an accidental introduction, his hebridensis 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 these specimens from true hebridensis. 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, TJ^ 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. 5 32). In average size the skulls are slightly 

 smaller than in typical hebridensis (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 h. Jtebridensis, 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 X.o \.y^\c2\ hebridensis ; 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 Eigg, 29th 

 March 191 3, by Mr P. D. Montague. Like the grass mouse of the 



