174 BULLETIN NO. VII. 
double-spring steel, smoothed-jawed trap, is placed in a breech 
in the dam and is intended to catch the unconscious repairer 
by the hind foot, as the fore foot would be torn away or severed 
by the teeth. Traps are also frequently set at the opening of 
the lodges or burrows, or even in frequented run-ways. The 
usual practice is, where possible to arrange the ring at the end 
of the chain so that it will slide downward upon an obliquely 
placed pole and drown the beaver, which instinctively dives 
when first discovering its peril. 
Sometimes gum camphor, castoreum or oil of juniper is used 
to attract beaver to the vicinity of the trap. A more destruc- 
tive method is sometimes employed. A party systematically 
drives the beaver from the lodges to the burrows, the mouths 
of which are then stopped, and the beaver are dug out and 
easily secured. The Indian resorts to a method requiring more 
patience and cunning. The pile of twigs gathered for food is 
barricaded, only a single opening being left. This is guarded 
by a twig, the movement of which apprizes the watcher of the 
entrance of the unsuspecting animal into the enclosure, which 
is now closed, and the beaver being confined under the ice soon 
drowns and is removed to make room for another victim. A 
single trapper can care for a line of thirty or forty miles. 
The beaver has been generally distributed over the wooded 
parts of the United States. The following quotation fromGeikie’s 
Geological Sketches will illustrate the conditions in many other 
regions: ‘‘The extent to which the valley bottoms in this and 
the other mountain ranges of western North America have been 
changed by the operations of this animal is almost incredible. 
In a single valley, for example, hundreds of acres are gradually 
submerged and their cottonwood or other tree-growth is killed. 
In this way the floor of the valley is cleared of timber. The 
beaver ponds, eventually silting up, become first marshes and 
then, by degrees, fine meadows.” 
In most of the wooded parts of Minnesota beaver were once 
abundant, but the traces of their existence are rapidly disap- 
pearing, and lodges can now be found only in the inaccessible 
regions far northward. 
Famity MURID~&. 
The North American Muride, according to Dr. Coues, may be 
characterized as follows : 
Dental formula: i. 4:}. c. 9:9 pm. 9:9 m. 3:3. Anteorbital 
foramen a large pyriform slit, bounded anteriorly by a broad 
