DESCRIPTION OF A SPECIES OF ARVICOLA. 425 
It resides in holes of its own digging, in the grassy banks 
of brooks and rivulets, feeding upon vegetable substances. 
In structure, form and habits, it closely resembles the Com- 
mon Water Kat ; but in colour, and certain other less 
palpable traits, it differs from that species, as much at least 
as the Black Rat differs from the Brown Bat, or the latter 
from the Mus giganteus. To the superficial observer, it 
has little of the aspect of a rat, its black colour giving it 
at a distance the appearance of a mole. Had I merely in- 
spected a skin or two, I should have hesitated to speak 
decidedly as its claims for specific distinction ; but having 
seen several hundred individuals, and handled at least a 
dozen, I may be allowed to introduce the animal to the 
notice of naturalists. 
The following description is applicable to the male and 
female. 
The head is short, broad, rounded, and slightly con- 
vex above ; the body thick and heavy, nearly cylindrical, 
tapering from the lower part of the belly to the tail ; 
the limbs small, their extremities delicate ; the tail longish 
and slender. 
The snout and nostrils are small ; the canine teeth, as 
usual in the order, large and apparent externally ; the eyes 
small ; the external ears entirely concealed in the fur, mem- 
branous, erect, broad, rounded, of moderate size, inter- 
nally bare, excepting at the margin, slightly covered exter- 
nally with extremely soft fine hairs. The meatus is very 
large, and capable of being exactly closed by a thin angular 
operculum, with a thickened margin. ^ 
The fore feet have five toes. The first toe or pollex is 
very small, with two phalanges, the claw alone appearing 
externally ; the second nearly equal to the fourth ; the third 
a little longer ; the fifth much shorter than the fourth ; all 
with three joints. The claws are slightly curved, very 
