(7. S. P. R. R. EXP. AN\> SURVEYS ZOOLOGY GENERAL REPORT. 



reflection ; this passes very insensibly on the lower parts into a dark plumbeous ; the tail of the 

 same plumbeous cast ; the feet tinged with brown. 



In a specimen from Sweden, on the other hand, the upper parts are not quite so sooty ; the 

 plumbeous of the belly is of a grayer shade ; the line of separation on the sides quite distinct. 

 This coloration is seen also in specimens from San Diego. 



This rat once better known than the brown rat, is rapidly diminishing since the introduction 

 into its haunts of the latter species. Its original locality is not well known, as from time 

 immemorial it has been the "house rat" of Europe, and of the warmer parts of the world 

 generally. According to Erxleben, it was brought to the New World about the year 1544, and 

 spread to such a degree as to have been apparently more abundant there than in the Old World. 

 Indeed, many authors have insisted that the species came originally from America, but there is 

 no foundation for such a supposition zoologically ; and it is spoken of familiarly by such authors 

 as Gesner, Aldrovandus, Seba, and others, at as early a date as 1550. 



The black rat is not mentioned by Burmeister among the animals of Brazil, where the Mm 

 decumanus, leucogaster, and tectorum, are abundant. 



In their article on the black rat, Audubon and Bachm,an refer to a white bellied variety of 

 the black rat, from the Edisto river, in South Carolina. This is most probably the Mus tectorum, 

 described in the next article. 



I have satisfied myself, from actual examination of the skin and skull of the original Mus 

 americanus of DeKay, that it is really a Mus, and of the present species. 



List of specimens. 



1 Body, 7 ; tail, 7J. 

 8 Body, 8 ; tail, 6|. 



