178 THE SCOTTISH NATURALIST 



Apodennis fridariensis thuleo, subsp. n. 



Habitat. The island of Foula (the Ultima Thule of 

 Tacitus). 



Material examined. Fourteen skins, twenty-two in 

 spirit, and a skeleton; collected by Mr W. H. Greenaway 

 and the Rev. J. Robertson. 



Type. An adult female, collected November 1917 ; 

 original number, 5. 



Description. In general external appearance this 

 animal closely resembles A. f. fridariensis but differs in its 

 smaller size and larger hind-feet. 



Size small, the head and body measurement being 

 scarcely greater than in A. sylvaticns and therefore con- 

 siderably less than in A. f. fridariensis. The tail is about 

 equal to the head and body in length when all the specimens 

 in adult pelage are averaged ; but it is slightly shorter 

 relatively in the larger or older specimens. The hind-foot is 

 very large, its absolute size being as great as in A. hirtensis 

 (the St Kilda Field Mouse), while its relative size is larger 

 than in any other British form. The sole-pads are small as 

 in fridariensis. 



In colour the Foula Field Mouse agrees exactly with 

 typical fridariensis. The flanks are dark, the lateral line of 

 demarcation being regular and sharply defined. The ventral 

 surface is of a dull bluish white, without any trace of a buffy 

 suffusion. Normally there is no trace of a pectoral spot. 

 The tail is strongly bi-coloured, dusky above, white below. 

 Dorsal surfaces of feet white. 



A direct, comparison of the skulls suggests a closer 

 affinity between A.f. tJmleo and A. f. grantii than between 

 the former and true fridariensis. The bullae are as small, 

 and the masseteric plate projects as little anteriorly as in 

 A. f. grantii ; while the brain-case appears to be still broader, 

 rounder, and more depressed than in the latter sub-species. 

 In the mandible the coronoid process is very feebly 

 developed as in each of the two sub-species oi fridariensis 

 hitherto known ; but its angular process shows no trace of 

 the remarkable elongation characteristic o{ f grantii. 



The measurements confirm these impressions derived 



