INTRODUCTION 9 



lived in this sea were only such as would be expected in waters of 

 warm temperature. Its tributary rivers could have been neither 

 large nor swift-flowing, since the sediment at its bottom was free, 

 or nearly free, from in-brought material. This was at least the 

 case not very far from its shores. Its slowly falling sediment was 

 composed, almost exclusively, of microscopic shells of animals 

 and plants, foraminifera and coccoliths. The deposits thus made 

 are almost identical with those now forming in various parts of 

 the world in clear but not deep waters, away from the immediate 

 coasts of the continents, almost pure chalk. Animals dying in 

 this inland sea fell slowly to the bottom during or after decomposi- 

 tion of their softer parts, and the slowly increasing sediments 

 covered up and buried the preservable parts. The many preda- 

 ceous fishes and other scavengers with which the waters abounded 

 often tore the decomposing bodies apart, separating and displacing 

 the bones of the skeleton; and the currents of the shallow waters 

 washed others apart. Often the teeth of fishes and other carnivorous 

 animals are found imbedded in the bones, and many are the scars 

 and toothmarks observed in the fossil bones. 



After the ocean had dried up and the bottom had been raised 

 far above the present level of the oceans, other deposits made in 

 lakes and by the winds covered deeply the consolidating sediments, 

 burying them for millions of years with all that they contained. 

 Long-continued erosion by winds and rains has again laid bare 

 many parts of the old ocean bottom, and has washed them out 

 into ravines and gullies. Many hundreds of square miles of this 

 chalk are now laid bare in western Kansas, upon which the growth 

 of vegetation has been prevented by the arid climate. Here and 

 there may now be discovered protruding from the sloping or pre- 

 cipitous surfaces of this exposed chalk bones or parts of bones of 

 the old animals buried so long ago in the soft sediment of the ancient 

 ocean bottom. 



The sharp-eyed searcher after fossils detects these protruding, 

 often broken and weather-worn, petrified bones, which themselves 

 betray the presence often of other parts of their skeletons still 

 concealed in the chalky hillside. Fortunate is he if he has dis- 

 covered a specimen soon after it appeared at the surface, before 



