ON A COLLECTION OF MICE FROM ST. KILDA 3 



The dimensions of the specimens measured from spirit 

 differ slightly from those of the present series, a discrepancy 

 which may be due to methods of preparation. It is remark- 

 able that all the sets of wild mice should differ from the true 

 House Mice in showing a slightly shorter tail. 



Jllns inumlis and J/. ;;/. faroensis are clearly robust 

 developments from the Mus musculus stock, the robust form 

 being accompanied by a very distinct colour pattern tending 

 in the same direction in both cases, but very much more 

 marked in J/. muralis. 



Mus Jiirtensis. As regards coloration this form is 

 evidently not so " fixed " to type as Mus muralis, since the 

 underside varies in colour from specimens with the whole 

 surface buff to those which exhibit only a strong staining 

 of this colour, most deeply on the central line, the latter 

 arrangement being that which obtains in J/. hebridensis. 

 But all are quite distinct from ordinary British sylvaticus. 



The following table exhibits the dimensional distinctions 

 of the various British forms of Field Mice : 



H. and B. Tail. Hd. ft. Ear. 

 Average of 10 Jiirtensis, 



5^s and 5 9s. . 104 100 24-7 16-25 



Average of 4 hebridensis . 108 97-5 24-25 15-75 

 Average of 62 , 



intermedius . 92-6 88-2 22-6 15-4 



Average of 4 wintoni IIO -75 m-75 2 3-75 18 



i from Shetland . . 102 100 22 15-5 



Average of 6 celticus . 85-3 80-8 22-3 14-6 



Apart from its colour J\I. Jiirtensis is thus shown to be 

 a robust form, excelled in general size only by wintoni, and 

 agreeing with hebridensis except in regard to its larger ear. 

 These two mice are thus closely allied : their large feet 

 exceed even those of the giant wintoni, while their ears, on 

 the other hand, especially in hebridensis, approach the lesser 

 dimensions of intermedius. Beside them celticus appears as 

 quite diminutive. 



In view of the approaching publication of my book on 

 British Mammals, I propose to leave unattempted here any 

 discussion of the relationship of these forms or of their 

 title to be accorded full specific rank. It seems hardly 

 doubtful, however, that were they animals of such a size as 



