NORTH AMERICA AND THE WEST INDIES 73 



are not easily trapped and usually remain the longest where they 

 do real damage, while in the higher mountains where they can 

 do no damage they are easily caught and quickly destroyed. " 

 While from an economic standpoint beavers may do some 

 damage to forest growth and even to crops, as in the case just 

 noted, by feeding on cornstalks, nevertheless this is easily con- 

 trolled. Bailey mentions that in 1910 the water company of 

 Santa Fe was offering $50 a pair for live beavers to be placed 

 in the upper part of the Santa Fe Canyon to aid in conserving 

 the city's water supply. He adds : "On almost all the mountain 

 streams they should be protected and encouraged. A series of 

 beaver ponds and dams along the headwaters of a mountain 

 stream would hold back large quantities of mountain water 

 during the dangerous flood season and equalize the flow of the 

 streams so that during the driest seasons the water supply 

 would be greatly increased in the valleys. Beaver ponds not 

 only hold water but distribute it through the surrounding soil 

 for long distances, acting as enormous sponges as well as 

 reservoirs. A series of ponds also increases the fishing capacity 

 and furnishes a safe retreat for the smaller trout and protec- 

 tion from their enemies . . * . A legitimate amount of 

 trapping should eventually yield large annual returns over 

 extensive areas of the country from which they have been 

 almost exterminated." 



MICHIGAN BEAVER; WOODS BEAVER 

 CASTOR CANADENSIS MICHIGANENSIS Bailey 



Castor canadensis michiganensis Bailey, Proc. Biol. Soc. Washington, vol. 26, p. 192, 

 Oct. 23, 1913 (Tahquamenaw River, 5 miles above falls, Luce County, Michigan). 



This is a very dark race of beaver, with a short, broad skull. 

 According to its describer, it is dark umber-brown above, 

 brighter on head and cheeks; ears, feet, and nose black. Under 

 side darker than back, with blackish on the breast and flanks. 

 The skull has the rostrum shorter and the nasals more quadrate 

 than in typical canadensis, the zygomata abruptly spreading, 

 the occiput with an upright crest, giving a short, "sawed-off " 

 appearance. Though said to be of small or medium size, the 

 measurements given do not show this: Total length, 1,170 mm.; 

 tail, 470; hind foot, 185; skull, condylobasal length, 129; 

 zygomatic width, 96.4; nasals, 46 by 24 (type skull). 



