36 
ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 
minute dark hairs : the tail is long and slender, and has small, scattered, 
bristly hairs, of a brown-black colour. 
Length from nose to root of tail 
of tail 
of tarsus . 
In. Lines. 
7 0 
6 6 
1 si 
Length of ear 
from nose to ear . 
In. Lines. 
0 7 
1 6 
No. 2. Hairs along the centre of the back chiefly black, and but obscurely 
annulated, near the apex, with deep yellow : towards the sides of the body, 
and over the haunches, the hairs are more distinctly annulated, and on the 
sides of the body they are of a pale yellow at the apex : on the under parts 
the hairs are gray, tipped with dirty yellowish white : the feet are of the 
same deep purple-brown hue as in the specimen first described. 
Habitat, Ascension Island, Atlantic Ocean, {July.) 
These two animals not only differ in the colour of the fur, one being of a 
grizzled brownish colour, and the other black, but there is a considerable difference 
in the texture of the fur. In the black specimen, the fur is very soft and glossy, 
and the long hairs, which are abundant, are very slender. In the brown specimen, 
the fur is of a harsher nature, the long hairs are not so abundant, but longer, and 
less slender. On the other hand, they agree in size, dentition, the length of the 
head, tarsus, and ears, and differ but in a trifling degree (about three lines,) in the 
length of the tail. 
Upon comparing the Ascension Island specimens with M. Rattus, I find 
that, although in size they are about one third less, yet the teeth precisely agree, 
not only in form, but in size. The relative proportions of the head, ears, and 
tarsi, also agree. Besides the general colouring of the fur, they both differ in 
having the hairs of the feet uniformly purple-black, those in Mus Rattus being 
much paler, and even whitish, on the toes. In the character of the fur, there is 
much difference. The long silky hairs, which are so conspicuous in Mus 
Rattus, are replaced, in the black specimen, by hairs which are scarcety to 
be distinguished from the ordinary fur; and in the other specimen, although 
rather longer and more distinct, they are short, compared with those of the 
black rat. 
“ The specimen which has a black, and glossy fur, frequents the short coarse 
grass near the summit of the island, where the common mouse likewise occurs. 
It is often seen running about by day, and was found in numbers, when the 
island was first colonized by the English, a few years since. The other, and 
browner coloured variety, lives in the out-houses near the sea-beach, and feeds 
