542 MURID^— APODEMUS 



the crofts. Some fine specimens were captured in a store close to the 

 water's edge. On the island of Dun it was found dwelling in fissures 

 and holes on the face of the rocks, where the very luxuriant grass was 

 growing close by on ledges or at the foot of the crags. Here its 

 presence was betrayed by its numerous runs, and by the seeds of grass 

 on which it feeds. Seeds of Carex flava were found in a hole a few 

 inches deep on a hillside in Hirta; these seeds form perhaps the 

 chief food. It appears to be much addicted to cannibalism ; because of 

 this, many specimens were completely destroyed before the traps could 

 be visited. It appeared to be entirely nocturnal. Like sylvaticus and 

 other mice, it attains sexual maturity at an early moment ; the nursing 

 females caught in September rgio and 191 1 varied greatly in size, 

 some being evidently quite young creatures. In September 1910 no 

 pregnant females and no young smaller than half-grown were taken. 

 In September 191 1 Mr Eagle Clark obtained several quite young mice. 

 A female caught on 14th September contained seven foetuses; another 

 younger one taken on the 1 8th, had six less developed foetuses. Mr 

 Waterston describes two nests, " neither of them typical." He found 

 males twice as numerous as females. Dissections showed the average 

 number of foetuses to be six. Both sexes appeared to be subject to 

 disease, especially of the liver, which was spotted by colonies of 

 coccidia, and also infested by a Cestode. The people said that on Dun 

 these mice are subject to variation in colour, and one with some white 

 markings was brought to Mr Waterston. 



THE FAIR ISLE FIELD MOUSE. 



APODEMUS FRIDARIENSIS (Kinnear). 



Synonymy under sub-species. 



Distribution : — Fair Isle and Shetland Islands, where it occurs on 

 Yell, and possibly on Mainland. 



History and status: — This Field Mouse was discovered on Fair 

 Isle by Kinnear, who described it in 1906 as a sub-species of A. sylvaticus. 

 In his Catalogue Miller has accorded this form full specific rank. 

 The differences between fridariensis and sylvaticus are scarcely such as 

 would entitle the former, if it stood alone, to be considered as anything 

 more than a sub-species of the latter. In the summer of 1913, 

 Ogilvie-Grant found a Field Mouse living on the island of Yell. 

 His specimens, although differing from typical fridariensis in some 

 respects, are clearly more nearly related to the Fair Isle mouse 

 than to A. sylvaticus, and they have been described as a sub-species 

 {A.f.grantii). A large Field Mouse also occurs on Mainland, Shetland, 

 and this, when better known, will probably be found to belong to 



