370 IVORY AND THE ELEPHANT 



beds of Nebraska are fully explored and studied, they are 

 destined to furnish satisfactory solutions to many of the 

 problems relating to the Proboscidea, and it is certain that 

 many new forms will be added to the list. 



Of all the creatures which have lived, but a moiety has 

 been preserved. After a few years not a vestige remains of 

 those skeletons which bleach in the open, while the few 

 dropped in mud and water may become buried and min- 

 eralized. Associated with the elephant bones are the re- 

 mains of such contemporaneous creatures as the rhinoceros, 

 camel, early horse, giant hogs, deer, and countless smaller 

 forms. Great predatory beasts, such as the sabre-toothed 

 cats and huge dogs, were their natural enemies. The cli- 

 mate was favourable, and vegetation must have been luxuri- 

 ant. Quantities of petrified wood bear evidence of the 

 forest vegetation of the time. 



ENTOMBMENT 



During the mastodon age in Nebraska, deep river and 

 lake conditions prevailed. The rivers which flowed in 

 ever-varying channels deposited gravels over broad areas. 

 There were wide meanders, lagoons, and marshes, and large 

 lakes and ponds. At flood time enormous amounts of 

 sand, gravel, and mud were spread over the country. In 

 periods of drought this could be assorted more or less by 

 wind. For this reason we often find aqueous and aeolian 

 deposits alternating. 



Herds of tropical animals frequented the water courses 

 and the rich vegetation bordering the lakes and lagoons. 

 Many of them perished in the water or were subsequently 

 swept in by freshets. Buoyed by gases of decay, their 

 carcasses floated until deflected into some cove bj'' wind or 

 water currents. They became stranded here, and their 

 skeletons were finally deeply buried in sand and mud. 



