Voles from the Inner Hebrides, Scotland. 365 



Nine collected by Mr. D. Anderson : — 



No. 01, male, 13th Juno, 1913 . . 

 No. 63, „ 16th „ „ 

 No. 64, „ „ „ „ 

 No. 71, „ 19th „ „ 

 No. 72, male, juv., 19th June, 1913 

 No. 60, female, 13th June, 1913. . 

 No. 62, „ „ „ „ . . 



No. 68, „ 18th „ „ .. 

 No. 69, „ „ „ „ . . 



Judging from tlie skulls the specimens Hinge from imma- 

 ture to young adult. None are really fid. 



External characters. Havinp; regard to the ap-e of the 

 specimens this new form agrees in size and proportions with 

 M. a. exsid, from which, however, it differs strikingly in 

 pelage. The general colour of the back is about as in e.vsnl, 

 but the rump and flanks are much darker ; the underside and 

 the posterior surface of each hind leg are silvery, in sharp 

 contrast with the dark brown of the flanks and rump. 

 Rarely the underside shows faint traces of a median stripe of 

 yellowish wash. The fur is longer and rather coarser in 

 texture than in exsul, giving the animal a shaggy instead of 

 a sleek appearance; this and the darkening of the rump and 

 flanks is due to the greater abundance and length of the 

 black "bristle" hairs. These features are conspicuous in 

 both vernal and sestival specimens. 



Dental and cranial characters. In enamel-pattern the cheek- 

 teeth of mial agree with those of exsul : in the nineteen cases 

 examined only one was entirely without a trace of the fourth 

 inner angle iu ch. t. 1 ; in three this structure was represented 

 merely by a microscopic vestige ; in eleven it was small but 

 quite distinct; and in four it was large and of regular form* 



Nine skulls admit of detailed investigation : their condylo- 

 basal lengths range between 25*4 and 27*4 mm., and the 

 condition of their temporal ridges &c. is such as to indicate 

 that, as in exsul and other subspecies of agrestis, the condylo- 

 basal length in old specimens must amount to 28'5 mm. or 

 more. Compared with skulls of exsid of equal age, that of 

 mial agrees closely, differing only in having the nasals rela- 

 tively a little shorter, the auditory bullae slightly smaller, 

 and the basioccipital, which, of course, is in close relation 

 with the bulla?, slightly shorter. These differences are made 

 clear in the following table : — 



