48o 



MURID.E— ARVICOLA 



in size), and each with its long axis parallel to that of the body.^ Their 

 slightly raised surfaces are closely and irregularly wrinkled so as to 

 present a honeycombed appearance, caused by a series of pits, from 

 the cavities of which arise hairs resembling those of the ordinary 

 pelage ; these hairs become scarcer towards the centre of the glands, so 

 that they may sometimes appear to be naked ; in dried skins their 

 positions are indicated by the grease-soaked fur. These glands recall 

 those of the shrews. 



The fur is close, dense, and long ; the underfur thick and woolly. 

 The colour (when not melanic) is normally dark brown, varying 

 from " broccoli-brown " to " mars-brown " or darker, deeper along the 

 back, lighter but not decidedly yellowish on the face and sides; the 

 cheeks not in contrast with the surrounding parts. The sides are 

 usually somewhat "lined" with black. The chest and belly vary 

 between ochraceous-buff and slate-grey, the latter derived from the basal 

 portions of the hairs. The feet are some shade between " hair brown " 

 and '' ecru drab," sometimes blackish ; the tail is blackish, the under- 

 side sprinkled with greyish hairs. 



There are two irregular moults, the summer coat being shorter and 

 often redder, owing to the absence of the long hairs with dark tips. 

 The post-juvenal coat of the young resembles that of the adult in summer. 

 The skull is large, with prominent ridges when old, and, as compared 

 with that of Microtus, the occiput and rostrum 

 tend to be obliquely truncate instead of nearly 

 vertical; the nasals at their widest region (in 

 front) are conspicuously narrower than the ros- 

 trum ; the incisive foramina are much shorter 

 and narrower; the auditory bullae are relatively 

 small ; and the basi-occipital wide. 



In the teeth the upper incisors, which are 

 anteriorly deep yellow, are not conspicuously pro- 

 jecting ; compared with those of Microtus they are 

 somewhat straightened and protruding, but to a 

 much less extent than in the scherman group. The 

 cheek-teeth (PI. XXVIII.) are large and heavily 

 built, the enamel-pattern well defined and distinct, 

 with sharp and definite angles ; the base of % 

 forms evident protuberances on the lower surface of 

 the mandible in old individuals. 11^ is simpler than in Microtus ; the 

 anterior loop is followed by a small outer and a larger inner closed 

 triangle ; the terminal loop is simple ; a third closed external triangle 

 is sometimes isolated ; this tooth has on each side normally three salient 



^ Adams kindly examined a number of individuals for these glands ; he finds 

 that they occur in both sexes. 



Fig. 79. — Dorsal View 

 OF Adult Skull of 

 A rvicola amphihius ; 

 natural size. (Drawn 

 by M. A. C. Hinton.) 



