VOL. VII, PP. 159-174 SEPTEMBER 29, 1892 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



DESCRIPTION OF A NEW GEXUS AND SPECIES OF 



MURINE RODENT (XEXOMYS NELSONI) 



FROM THE STATE OF COMMA, 



WESTERN MEXICO. 



BY C. HART MERRIAM, M. D. 



Among the many interesting mammals recently collected by 

 Mr. E. W. Nelson in western Mexico is a handsome rat-like 

 rodent which seems to he not only an undescrihed species, but 

 the type of a new genus. In form and general external appear- 

 ance it looks like a rather small wood rat of the genus Neotoma, 

 but differs from the members of that genus, and in fact from all 

 other known North American murines, in having a large and 

 clearly defined whitish spot over each eye and another (though 

 less conspicuous) below each ear. The upper lips and cheeks 

 also are white more than half way to the eyes, giving the animal 

 a very pretty as well as unusual physiognomy. The color of 

 the back and upper parts generally is deep tawny red or fulvous, 

 while the under parts are creamy white. The skull and teeth 

 present a combination of characters so unlike those of any known 

 rodent that a new genus must be framed for its reception. While 

 resembling Neotoma more closely than any other genus, it differs 

 from it in many important characters. With a skull much 

 like that of Neotoma incxicana, it has well developed supraorbital 



2-J-Bioi.. Sin'. WASH.. Vm,. VII. ltf'12. (159) 



