MILLER: MAMMALS OF ONTARIO. 
25 
Peromyscus canadensis canadensis is a larger animal than P. c. 
umbrinus. Ten adult male topotypes of the former average: total 
length, 191.5 ; tail vertebrae, 98.1; hind foot, 21.2 ; ear from meatus, 
18.2. Ten adult female topotypes average: total length, 183.3; 
tail vertebrae, 92.3; hind foot, 20.9; ear from meatus, 18.4. De¬ 
tailed measurements of 100 specimens of the typical form are given 
in the original description. 1 
a Skull and teeth. — In cranial and dental characters Peromyscus 
canadensis umbrinus agrees closely with P. canadensis canadensis. 
Both skull and teeth are slightly smaller than in the typical sub¬ 
species, but the differences are no greater than might be anticipated 
from the relative sizes of the animals. The skull of Peromyscus 
canadensis umbrinus is distinguished from that of P. texensis arcti- 
cus by its more slender form, lighter and longer rostrum, and less 
abruptly flaring zygomata. 
General remarks. — In color and external appearance Peromyscus 
canadensis umbrinus resembles P. texensis arcticus more closely 
than it does P. canadensis canadensis. It is easily separated from 
any of the forms of texensis , however, by its proportionally longer 
tail and differently shaped skull. From P. leucopus it differs in 
proportions and color, but is apparently the form of canadensis most 
closely resembling leucopus. As compared with autumnal specimens 
of P. canadensis canadensis , P. canadensis umbrinus differs in 
darker tail and ears, darker face markings, slightly darker and 
richer ground color of back, and conspicuously greater darkening of 
back resulting from admixture of black-tipped hairs. As a rule the 
belly in umbrinus appears to be less snowy white than in canaden¬ 
sis, , as the plumbeous under fur shows through more distinctly on 
the surface. 
Mus Museums Linn. 
The house mouse is common at North Bay, but does not occur at 
Peninsula Harbor or Nepigon. 
Mr. Brooks found it abundant at Mount Forest and Milton. 
In 1830 Gapper wrote of this animal: “Very common all over 
the country [between York and Lake Simcoe]. A great many are 
frozen to death in the barns, where the native mice live in perfect 
security.” 
ij’roc. Biolog. Soc. Washington, 1893, vol. 8, p. G7-G9. 
