20 Bulletin Wisconsirt 'Xatural History Society. [Vol. 6, Nos. 1 — 2. 
lodges are quite frequently encountered, and some of them appear 
to have been quite recently built. There are a few beavers still 
remaining in some of the more secluded portions of the state, and 
it is hoped that sufficient protection will be given them tO' prevent 
their extermination. 
There are two skulls of Castor canadensis in the collection of 
Dr. H. V. Ogden ; one of these was taken in Sawyer County, No- 
vember 3, 1899 : the other was taken in Iron County, October 8, 
1903. 
Mus musculus LiniiEcns. 
House Mouse. 
House mice are common around dwellings and barns over the 
entire state. In the southern part of the state they are found in 
nearly every cornfield and grassy meadow, and I caught two spe- 
cimens in traps set for shrews in a wet marsh. Apparently not 
increasing in abundance. 
Mus norvegicus Erxleben. 
BrowTi Rat. 
This mammal is too well known to need discussion. Rats are 
found everywhere in the state, but are less abundant in the north- 
ern sections. I have observed them in the cornfields in Rock 
County; this is the only locality where I have found them any 
distance from buildings. Mr. J. N. Clark reports them occurring 
"to some extent in fields in summer and fall" in Dunn County. 
Peromyscus canadensis (Miller). 
Canadian Deer Mouse. 
My specimens of Peromyscus from the pine regions of north- 
ern Wisconsin have been determined by Mr. W. H. Osgood to be 
canadensis and not the sub-species umbrinus. All the specimens 
that I have taken average slightly smaller than typical canadensis 
and in this respect approach umbrinus, but their color compares 
favorably with canadensis. Average measurements of three 
