NORTH AMEHICANl FAUNA 66 



Figure 35. — Distribution of Peromyscus leucopus noveboracensis. 



Distinguishing chardcteristics. — The white- footed mouse closely re- 

 sembles the deer mouse {Peromyscus mamiculatm) , from which it may 

 be distinguished as follows : 



From Peromyscus m, hairdii it differs in being larger, longer tailed, 

 lighter and more brightly colored with more reddish on sides and back, 

 and in having noticeably larger ears and feet; the tail is less distinctly 

 bicolored. 



Cranially, P. I, novehoracensis is larger than P. m. hairdii^ and the 

 incisive foramina are differently shaped. These foramina are anteriorly 

 constricted in noveboracensis, and open and evenly curved in hairdii. 

 A detailed comparison of these two forms is given by Stickel (1951, 

 p. 25-32). 



From Peromyscus m. nuhiterras, P. I. noveboracensis differs in being 

 larger, shorter tailed, (tail less than half the total length of the animal) 

 and more brightly colored, with more reddish on sides and back. This 

 color difference is subtle in individual specimens but becomes apparent 

 when large series of both species are examined. The tail in novebora- 

 censis is less distinctly bicolored than in nubiterrae. 



Some specimens of nuhiterrae and leucofus are so similar in external 

 characteristics that only by a detailed examination of the skull can they 

 be separated. The skull of nubiterrae is slender and elongated, the 

 braincase considerably flattened, whereas cranially novebora/)ensis is 

 broader and heavier with the braincase more inflated. As in P, m. 



