MUS SETIFER/ 
setifcr, and associates our animal naturally with those species, which, in the article 
Mammalogie of the Encyclopedic, constitute the second section of this genus. It is 
however to he remarked, that these hairs are not of a spinous nature, as in the Mus 
fasciculatus and the Mus macrourus; they may properly be compared to bristles, 
having more consistence and rigidity than those of the Mus decumanus and giganteus; 
and in a natural arrangement, our animal stands between these species, and between 
those from which the chapter of the section is derived by M. Desmarest, and 
which, in a more rigorous sense, may be called spinous Rats. 
Our animal agrees in many particulars of its form and proportions with the Mus 
decumanus, the Brown or Norway Rat; but it is larger, and more robust. The head 
is lengthened, and somewhat depressed. The nose is acute, and marked above with a 
longitudinal ridge of delicate hairs, while the extremity, in which the nostrils are 
situated, is naked : it is well calculated for burrowing the ground. The upper Up is 
deeply divided ; the lower hp is considerably shorter than the upper, and the front 
teeth, in both jaws, are largely exposed; their colour is reddish-brown, and more 
intense in the upper jaw. These teeth are proportionally larger, and more robust 
in our animal than in the Mus decumanus ; they are broad, strongly curved, attenu- 
ated in form of a chisel, and abruptly terminated, exhibiting very powerful cutting 
edges. The grinders, nearly resembling those of other Rats, are disposed in a per- 
fectly regular series ; they are transversely grooved above, and marked at the sides 
with stria?, or depressions. The eyes are small, vivid, and prominent. The whiskers 
are black and numerous, arising promiscuously from a large portion of the cheeks. 
Above the eyes, and near the temples, a single bristle arises from a separate point. 
The ears are long, broad, rounded, and covered towards the margin with a very 
minute down ; the extent of the external lobe exceeds that of the Mus decumanus ; 
several transverse divisions are observable in the interior. 
The body of the Mus setifer is robust, lengthened, and cylindrical. In the 
proportion of the extremities to the body, our animal resembles the Norway Rat. 
The fore feet (in our specimens) are comparatively slender and weak ; the thighs, in 
the posterior extremities, are remarkably robust. The feet are covered with hairs to 
the extremity ; they are five-toed ; in the fore foot the thumb is very minute, con- 
sisting of a somewhat lengthened compressed claw, removed far from the other toes, 
and supported by a tubercle, which when dried, acquires a corneous appearance ; the 
other toes have the same proportions as the fingers in the human hand. The claws 
are slightly curved, obtuse, and apparently formed for perforating the ground. On 
