480 MURIDAZ—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 J/zcrotus, 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 bulle 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 JZzcrotus they are 
somewhat straightened and protruding, but to a 
Pere aiiouencnuiey much less extent than in the scherman group. The 
or ADULT SKULL or heek-teeth (Pl. XXVIII.) are large and heavily 
Arvicola amphibius ; built, the enamel-pattern well defined and distinct, 
natural size. (Drawn with sharp and definite angles; the base of mz, 
by M. A.C. Hinton.) forms evident protuberances on the lower surface of 
P 
the mandible in old individuals. 2* is simpler than in J/ccrotus ; 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 

1 Adams kindly examined a number of individuals for these glands; he finds 
that they occur in both sexes, 
OE 

