1915.] 



IXTRODITCTIOX. 



9 



Little mounds of earth., tlirown out as the buiTows are excavated; 

 and varying in bulk normally from a quart to a bushel and in dis- 

 tance from a close proximity to 15 feet apart, mark the lines of the 



B 2042-1 22 



FxG. 1.— Map showing the distrihution of the genu.? Thomomys (shaded area . 



burrows. After the loose soil is pushed out, the openings are securely 

 packed with earth and closed from within as a fortification against 

 enemies. The entrances are often closed so secm'ely that even the 

 experienced trapper has difficulty in locating the bmrow beneath. 



