LESSONS IN GEOLOGY. 359 



thecretaceous the first dicotyledons appeared, as the oak, willow, 

 maple, and sassafras, and became numerous, as many as 100 

 species having been discovered. And leaves of the redwood and 

 of the palm have also been discovered. 



The characteristic life of the age was reptilian, so that it is 

 often called the Age of Reptiles. They practically appeared with 

 the age, reached their culmination and passed into a decline. 

 They were very large and very numerous, they dominated the 

 water and the land, and some were furnished with wings for ex- 

 cursions in the air. Invertebrate life was abundant, and so were 

 ganoid fishes and amphibians. In the cretaceous the teleosts, or 

 bony fishes, and birds of different kinds appeared, and remains 

 of mammals have been found in the triassic rocks. 



The famous chalk cliffs of England, and the cretaceous beds of 

 eastern North America, were doubtless formed at the same time, 

 and were continuous. These localities were raised above the sea 

 level, while chalk is still being formed in the ocean between. 



At the close of the Jurassic, there were some igneous eruptions 

 in the Connecticut Valley, and other slight disturbances on the 

 Atlantic coast; but the great revolution was the swelling up of 

 the then marginal sea bottoms into the Sierra Nevada and Coast 

 Range mountains, and doubtless theUintah and Wasatch ranges 

 began to rise about the same time. 



At the close of the cretaceous, or soon afterward, the whole 

 western half of the continent was elevated, the interior cretaceous 

 sea disappeared, the Rocky Mountain region joined the tableland 

 and the Appalachian region, completing the continent. 



The Cenozoic Era, or Age of Mammals, is divided into the Ter- 

 tiary and Quaternary Ages. 



The Tertiary Age is divided into the Eocene, or lower, Miocene, 

 or middle, and Pliocene, or upper tertiary. 



The tertiary deposits constitute the Atlantic and Gulf coast 

 plains, and extend from the Gulf up the Mississippi river to the 

 mouth of the Ohio river. These are marine deposits of a some- 

 what varied character. In the Rocky Mountain region there 

 are numerous basins of fresh-water deposits belonging to this 



