442 U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



The tail is rounded, and tapers gently to a truncate tip ; it is nearly two inches longer than 

 tho head and body, and has 237 annulations of scales. 



The fur of this species is composed of two kinds of hairs, one external, coarse and rigid, the 

 other shorter, finer, and intermediate. 



The color of this species above is much like that of the Norway rat, being of a yellowish 

 brown, slightly tinged with reddish on the sides of the back, and grayer on the sides. A 

 predominance of black hairs on the back imparts here a dusky appearance. The entire under 

 parts, with the upper surfaces of the feet, are quite pure yellowish white, to the very roots of 

 the hairs. The ears and entire tail all round are dusky. 



The only specimens of this species I have seen from America are those entered below, of 

 which one in alcohol (2811) has served as the basis of the present description. A specimen 

 received from Niirnberg, and probably caught there, has the long tail, but is not so white 

 beneath. It has 240 annuli on the tail. 



This species is smaller than the common rat, and the tail, instead of being shorter than the 

 head and body, is much longer. The under parts and feet are nearly pure yellowish white. 

 The ears are larger. 



The Mus leucogasier of Pictet, has the tail not quite so long, and the hairs soft, of equal 

 length, and without any intermixture of long stiff bristly ones. 



The roof rat, so called from its fondness for inhabiting the thatched roofs of houses, is origi 

 nally from Egypt and Nubia, from which it was taken to Italy and Spain. It is quite probable 

 that the early Spanish discoverers and conquerors carried it to America in their vessels, and 

 thus introduced it on the continent long before the brown or even the black rat. It is now very 

 common in Brazil and some parts of Mexico ; and if, as I have little doubt, the " light-colored 

 variety of the black rat" of Audubon and Bachman be this species, it is abundant in Georgia 

 and South Carolina, (according to Major Leconte, more so formerly than now,) and doubtless 

 also in Florida. It is said by Mr. Bridger to be very common about Tarboro', North Carolina ; 

 further north I have no knowledge of it. 



I have myself verified very few of the quotations at the head of this article, and am unable to 

 say why authors have retained the name of M. tectorum in preference to the apparently older 

 one of Geoffroy. The Mus americanus of some authors is, in every probability, this same species, 

 which, after its very early introduction into America, (probably in the fifteenth century,) became 

 naturalized, and, at an early date, was described by Seba as Mus americanus, probably from 

 South American specimens. The roof rat was not formally separated or distinguished as a 

 European species for nearly a hundred years after, and it is not difficult to understand that an 

 animal so conspicuously different from the Old World rats known at that time, and brought 

 from America, should have been described as new. The name of americanus has really priority 

 over either tectorum or alexandrinus, but is objectionable as conveying an erroneous idea of native 

 locality. 



