176 Firrtp Museum or Natura History — Zoétocy, Vor. XI. 
Part 2. Front of upper incisors (front teeth) without distinct groove near 
outer edge. 
Upper parts nearly uniform brown in color; tail not exceeding 1 inch in 
length and usually less. GREATER PINE Mouse. 
Microtus pinetorum scalopsoides, p. 222. 
Upper parts with wide chestnut dorsal stripe (down middle of back) in 
decided contrast to gray brown of sides; tail more than 1 inch long. 
RED-BACKED Mouse. 
Evotomys gapperi, p. 208. 
Subfamily MURINE. 
An Old World subfamily of which several species have been in- 
troduced into America. The characters as given for the following genera 
will answer our purpose here. 
Genus MUS Linn. 
Mus Linnzeus, Syst. Nat., X ed., I, 1758, p. 59. Type Mus musculus 
Linn. 
Front teeth (incisors) two in each jaw; no premolars; three molars 
or grinding teeth in upper jaw having tubercles on crowns arranged in 
three longitudinal rows; incisors narrow and without groove; 
crown of anterior molar larger than both the others combined; 
Boca third molar very small; edges of anteorbital foramen forming 
Upper Molars. a nearly perpendicular slit in front of zygoma; tail long and 
usually nearly naked and scaly; hind feet with five developed toes; fore 
feet with four developed toes and a rudimentary pollex with short nail. 
Originally this genus included the Old World Rats and Mice, which have 
been introduced in the United States, but is now restricted to a single 
species, the House Mouse, the Rats having been separated and placed 
in the genus Epimys. 
M. 3-3= 16. 
3) 
Dental formula: I. = C; = Pu. 
Ww 
Mus musculus Linn. 
House Mouse. 
[Mus] musculus Linnazus, Syst. Nat., X ed., I, 1758, p. 62. 
Type locality — Sweden. 
Distribution — Old World species, now generally distributed through- 
out the settled portions of the United States, about buildings and 
in cultivated fields and occasionally in unsettled districts. 
