FAMILY MURID.E. 79 



is also erected, and by a very sudden movement lie is enabled to strike, leaving the loosened 

 spines in the body of his opponent. From their peculiar structure, they penetrate at every 

 movement until they reach a vital part. Hence it is rarely attacked, although the hunters 

 easily kill it by a blow on its nose. The Indians esteem its flesh, which resembles young 

 pork very highly. It dwells in hollow trees, or in caves under rocks, and is said to bring forth 

 two at a litter in April or May. The spines are employed extensively by the Indians, after 

 having been dyed of various colors, to form ornaments for their dresses. 



The Porcupine is found as far north as 67°. It is found in all the Northern States ; in 

 New- York, Pennsylvania, the northern parts of Virginia, Kentucky, and through the western 

 regions to the Rocky Mountains. In this State, more particularly in the northern and western 

 counties, they are quite numerous. The first name given in accordance with the binary sys- 

 tem, is that proposed by Brisson, and by the law of priority it must be restored. 



FAMILY VI. MURIDJE. 



Clavicles robust, and fully developed. Fur not uniformly soft, but ivithout spines or rigid 

 hairs. Molars usually six above and six beneath, but various. Some of the genera are 

 provided with cheek pouches. Tail cylindrical, usually naked or sparsely haired, of 

 various lengths. Mostly composed of small burrowing animals. 



This family comprises numerous species, which are confessedly difficult to group together 

 by common characters. They may, however, be divided into two great sections, characterised 

 by the presence or absence of cheek pouches. Under those with cheek pouches, we arrange 

 the genera Geomys and Diplostoma. The other division embraces the genera Mus, Arvicola, 

 Sigmodon, Neotoma, Georychus, and Aplodontia. The field for discovery in this family is still 

 far from being exhausted. The representatives of only three genera are found in this State. 



GENUS MUS. Linneus. 



Molars six above and six beneath, with tuberculous summits. Tail scaly, nearly naked, 

 longer or nearly as long as the body. Ears usually naked or slightly furred. 



Obs. Three of the species have been introduced. 



THE BROWN RAT.— (Introduced.) 



MUS DECUMANUS. 



Mus decitinanus. Pallas. 



Brown Rat. Penn. Arct. Zool. Vol. 1, p. 130. 



Common Brown or Norway Rat. Godman, Am. Nat. Hist. Vol. 2, p. 78. 



Brown Rat. Richardson, F. B. A. Vol. 1, p. 141. Emmons, Mass. Report, 18-10, p. 63 



Characteristics. Grayish brown above, tinged with yellow ; beneath whitish. Tail not 

 quite as long as the body, and with 180 rings. Length 19-20 inches. 



