NATURAL SCIENCES OF PHILADELPHIA. 173 



SYNOPSIS' OF THE MTJEID^a: OF NORTH AMERICA. 

 BY DR. ELLIOTT COUES, U.S.A. 



Family MURID.E. 



Taken in its current acceptation, but witli exclusion of the 

 genus Jaculus, which differs sufficiently in dentition, in the cha- 

 racter of the anteorbital foramen, proportions of limbs, and other 

 features. 



1.1-=!; C. ^; P. 0- ; M. ^H^^ = tzi = 1 = 16 teeth. 

 11' 00' 0-0 ' 33 44 8 



Anteorbital foramen a large pja-iform slit, bounded exteriorly by 



a broad plate of the maxillary. 



Subfamily MuRiNiE. 



Molars rooted, tubercular, with crenate peripher^^ Koot of 

 under incisor causing protuberance on outside of jaw, at or near 

 notch between cond^'le and coronoid process. Descending pro- 

 cess of mandible a broad flattened plate, wholly below plane of 

 the molars. Anterior root of zj'goma deeply nicked at the ante- 

 orbital foramen. Palate nearly plane. 



Murine Series. 



Molars with three tubercles in transverse series. Soles naked. 

 (Only indigenous in the Old World introduced in the New.) 



Genus I. MUS, Linn., emend. 



1. Mus decumanus. 



2. Mus alexandrinus. 



3. Mus rattus. 



4. Mus musculus. 



' Abstract of a memoir in wliicli the characters of the varietie.s, species, 

 aud liigher groups are treated in full, with sjaionymy, bibliograpliy, etc., 

 and the argument for the views advanced. Based on the material (several 

 thousand specimens) in the Museum of the Smithsonian Institution. 



