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. 



FAMILY 



The North American Muridce, according to Dr. Coues, may be 

 characterized as follows : 



Dental formula: i. -}-:}. c. :$ pm. -:g- m. f :f. Anteorbital 

 foramen a large pyriform slit, bounded anteriorly by a broad 



