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6 MONOGRArnS OF NORTU AMERICAN RODENTIA. 



Diag«oi,lic table of .o»ie cranial and denial character, of Xorth American MtiiUD^-Continnoa. 



Subfamily MURIN J). 



Tlie characters of this subfamily having already been given in sufficient 

 detail for present purposes, we may at once proceed to consider its subdivision 

 into the two tribes or scries of genera ; namely, Mures and Sigmodontes. This 

 separation of the Old World (Mures) and New World (Sigmodontes) repre- 

 sentatives of the subfamily seems to us warrantcid, and not alone upon geo- 

 graphical grounds; for a decided difference in dentition is found, serving for 

 their immediate identification. ; 



Mures. — Molars of upper jaw, with the tubercles in three series. Palate 

 e.\tending back of the molars. (Palajogrcan.) 



Sigmodontes. — Molars of upper jaw, with the tubercles in two scries. 

 Palate ending opposite last molars. (Neogrean.) 



The Mures which occur in North America, — namely, four species 



