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winter climates the skin may be spread out on the snow and frozen flat 
and smooth, after which it may be hung up outdoors. In the dry, cold 
atmosphere of northern Canada, the moisture will evaporate rapidly from 
a frozen skin hung up exposed to the wind. In warmer regions the skin 
may be tacked or pegged out, or the corners held down by weights to dry. 
Beaver skins for the fur trade have the tail and feet trimmed off and 
the skin stretched in circular shape on a wooden hoop, the skin laced to 
the hoop by a thong passed through holes cut in the margin of the skin. 
The tail and feet of muskrats, and the flippers of seals, are also cut off 
before stretching. Such skins, however, are worthless for scientific pur- 
poses, except for showing condition of the pelt at the time of taking. 
Most natural history museums do not have adequate collections of 
the valuable fur-bearing mammals. Competent trappers are not often 
available, winter field work is difficult and expensive in the haunts of the 
rarer mammals, and high prices for fur prevent extensive purchases. The 
skulls of such mammals from different regions are of great interest 
to the zoologist for study of geographical races, and to the palaeontologist 
for comparison with fossil forms. Skulls of skinned mammals are a mere 
by-product of the trapping business, and are generally thrown away, but 
the National Museum will be grateful to any trapper who will take the 
trouble to donate skulls with data. 
