94 NEW YORK STATE MUSEUM 



Lower front teeth'long, their roots 

 extending under posterior grind- 

 ing tooth into outer side of jaw 



(voles) 



Tail flattened laterally (musk- 

 rat) Fiber, p. 101 



Tail round 

 Grinding teetli without roots 



(prongs) Microtus, p. 102 



Grinding teeth with roots 

 (prongs) in adults 



Grinding teeth heavy, 

 with sharp-pointed an- 

 gles ; color never red.. Phenacomys, p. 108 

 Grinding teeth light, with 

 blunt angles; color usu- 

 ally red .Evotomys,p. 109 



Genus Mus Linnaeus 



1758 Mus Linnaeus, Systema naturae, ed. 10.1: 59. Type Mus rattus 

 Linnaeus. 

 Front teeth without grooves ; cheek teeth in upper jaw with tubercles of crown 

 arranged in three longitudinal rows ; form slender ; tail long, scaly, scant haired ^' 

 fur coarse. (Lat., a mouse) 



The genus Mus contains many old world species, but none native to 

 America. Four have been naturalized in the United States. One of 

 these, the roof rat, Mus alexandrinus (like the black rat but 

 brown with a yellowish white belly) is normally confined to the lower 

 austral zone. Two of the three others are well known within our limits. 



SPECIES OF MUS 



Total length under 200 (8) (mice) M. musculus 



Total length over 300 (12) (rats) 



Color bluish black ; tail more than half of total length M. rattus 

 Color brownish; tailless than half of total length M. decumanus 



« 



Mus musculus Linnaeus House mouse 



1758 [M us] musculus Linnaeus, Systema naturae, ed. 10. 1 : 62. (Sweden) 

 Brownish gray, slightly paler below. Total length, 170 (6f) ; tail vertebrae, 

 85 (3f ) ; hind foot, 17 ( ). (musculus; Lat., a little mouse) 



The house riouse is thoroughly established throughout the settled parts 

 of America. It is abundant in buildings and cultivated fields within 

 our limits, and is sometimes found in woods. 



