REACTIONS ON LAND 



81 



Fig. 16. — A vertical section of a prairie-dog burrow (Cynomys ludovicianus Ord.) 

 showing the bringing of soil from a depth of nearly 5 meters. A, mound; 

 B, funnel-shaped entrance to bun-ow; C, main passage 4^/^ inches (11.4 centi- 

 meters) in diameter, about 15 feet (4.6 meters) in length; D, horizontal passage 

 9^/^ feet (2.9 meters) in length; E, unused nests filled with earth and refuse; 

 F, unused part of horizontal passage filled with earth, etc. 4 feet (1.2 meters) 

 long; G, niche large enough for one prairie dog; H, nest of grass 11 inches (28 

 centimeters) in diameter by 9 inches (22.8 centimeters) high; /, absorbent 

 matter carrying bisulphide of carbon; K, position of prairie dogs as found after 

 use of bisulphide of carbon; L, depth of horizontal passage 14 feet 7 inches. 



(After Merriam, 1901.) 



