162 MURIDJE. MURINJE. MUS. 



and the consequent angles and loops shown, more readily indicate 

 the relationship of their owner to other forms. Members of the 

 Muridce have a certain family resemblance to each other, in the more 

 or less lengthened tail, generally naked and scaly, bright eyes, and a 

 modest coloration suitable for concealing them from their foes. 



Fam. III. JIuri<l;i'. Rats, Mice, Voles, etc. 



Premolars none; molars with or without roots, tuberculate, or 

 with enamel folds; lower incisors compressed; frontals greatly con- 

 tracted anteriorly. 



Subfam. I. Murinae. 



Molars rooted, tuberculate; root of under incisor creating a swell- 

 ing on outer side of mandible between processes of the condyle and 

 coronoid; descending process of mandible below the plane of the 

 molars. Palate nearly flat. 



The genus M us, has more members than any other of the Mammalia 

 and its representatives are found throughout the world, except in 

 Madagascar, and possibly other islands whose faunae are unknown. 

 The habits of the various species are similar, although some are 

 arboreal and others even aquatic. 



4O. Mus. Mice, Rats. 



Mus Linn., Syst. Nat., i, 1758, p. 59; n, 1766, p. 79. Type Mus 



rattus Linnaeus. 



Ears large, prominent; tail long, scaly; nose acute; molars with 

 transverse series of tubercles, three in a series, longitudinal. 



KEY TO THE SPECIES AND SUBSPECIES. 



A. Size small ; tail moderately long. PAGE 



a. Pelage above grayish brown and black, 



beneath ashy plumbeous .................. M. musculus 162 



b. Pelage above black, beneath buffy gray ..... M. nt. jalapce 163 



B. Size large, tail very long, naked, scaly. 



a. Pelage black on upper parts .................. M. rattus 163 



b. Pelage brownish on upper parts. 



a/ Under parts ashy white ................ M. norvegictis 164 



b.' Under parts yellowish white .......... M. alexandrinus 164 



119. musculus (Mus), Linn., Syst. Nat., i, 1758, p. 62; n, 1766, 

 p. 83. Elliot, Syn. N. Am. Mamm., 1901, p. 118. 



