366 Messrs. Barrett-Hamilton and Winton on new 



M. a. mial. M. a. e.vsul. 



1. Oondylo-basal length 100 100 



2. Nasal length 26-2-27-3 28-0-30-0 



3. Distance between condyle and molars. . 39-8-42-3 39-6-42-1 



4. ,, „ „ anterior 



face of bulla 28-4-29-6 29-5-31-4 



5. Median length of basioccipital 13-8-15-9 15 3-17 8 



It is quite likely that when older skulls o£ mial come to 

 hand further distinctions from e.vsul will be found ; a sugges- 

 tion of this is afforded by the skull of the type, which has 

 the parietal region flatter than in any of the numerous skulls 

 of exsul before us. For the cranial dimensions see table on 

 p. 367. 



Remarks. M. a. mial is to be regarded as a peripheral 

 and local modification of M. a. exsul; in the Outer Hebrides 

 the latter, so far as is known, shows no tendency to be 

 differentiated into local races on the various islands which it 

 inhabits. 



3. Microtus agrestis luch, subsp. n. 



Hob. Muck, Inner Hebrides. "Very scarce; trapped in 

 short heather on the edge of the cliff" (Montague). 



Material examined. Three adults collected by Mr. P. D. 

 Montague. Dimensions : — 



Head and Hind 



body. Tail. foot. Ear. 



No. 72, male, 4th April, 1913 108 32 17-5 11-0 



No. 74 (type), male, 5th April, 1913. . 110 33 18 11-5 



No. 73, female, 4th April, 1913 .... 105 33 18 11-0 



In the skulls the temporal ridges are fused in the inter- 

 orbital region, and these animals are at least nearly of full 

 size. 



External characters. Size smaller than in other subspecies 

 of agrestis, nearly as in M. hirtus. The fur is dense and 

 shaggy, rather like that of mial, although this character is 

 less marked. The underside, including that of tail, has 

 throughout a heavy wash of buff or yellow, darkened here 

 and there by the slaty bases of the hairs. On the back the 

 black "bristle" hairs are nearly as abundant and as long as 

 in mial, and the colour is as dark as in the latter ; laterally 

 these hairs are fewer in number and shorter, so that the 

 colour of the flanks is lighter than in the Eigg form, and it 

 passes insensibly into the buff of the underside 



Dental and cranial characters. The cheek-teeth are normal ; 

 ch. t. 1 has no trace of a fourth inner angle. Save for its 



