26 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Mus decumanus Pall. 
The house rat was introduced through northern Nipissing and 
southern Algoma at the time of construction of the Canadian Pacific 
railroad, along the line of which it is now irregularly distributed. I 
saw no rats at North Bay or Peninsula Harbor, but found them 
abundant at Nepigon. They are said to occur at Heron Bay, a few 
miles south of Peninsula Harbor. 
Common at Mount Forest and Milton (Brooks). 
Capper wrote in 1830 that the house rat was then “found only in 
the warehouses near Lake Ontario/’ 
Castor canadensis Kuhl. 
At North Bay the beaver is locally common, and I saw a mounted 
specimen that had been killed near the town. At Nepigon they 
are said to be common, and at Peninsula Harbor I saw abundant 
signs of their work on the bank of a stream a few miles north of 
the station. 
In 1830 Capper wrote that the beaver is “now very rare [in the 
region between York and Lake Simcoe], though their old embank¬ 
ments are still to be seen on most streams.” 
Arctomys monax monax (Linn.). 
Mr. Brooks found the woodchuck abundant at Milton and Mount 
Forest. 
Not uncommon in the region between York and Lake Simcoe 
(Capper). 
Two melanistic adults taken by Mr. Brooks at Mount Forest and 
now in the Bangs collection are clearly referable to the typical sub¬ 
species, a form whose northern limit probably coincides very nearly 
with the upper edge of the Transition zone. These specimens were 
not measured in the flesh, but their long tails (130 mm.) distinguish 
them from the form inhabiting the north shore of Lake Superior. 
Arctomys monax melanopus (Kuhl) ? 
At North Bay woodchucks are said to be common, but during 
the summer of 1896 they were so scarce that I saw none. 
The woodchuck is common at Nepigon and Peninsula Harbor, 
but I was so unfortunate as to secure no adults. On the north 
