CHAPTER XLIX. 



THE MESOZOIC OR SECONDARY ERA, AND THE TERTIARY AGE. 



THE Mesozoic Era in Europe'shows three well-marked divisions, 

 which are known as the Triassic, Jurassic, and Cretaceous periods. 



The triassic and Jurassic are not as distinct in North America, 

 but the three periods are recognized. The triassic rocks are 

 mainly red sandstones, with some conglomerates, shales, and im- 

 pure limestones. They occur in Nova Scotia, Connecticut, enn- 

 sylvania, and North Carolina, and over wide areas in the Rocky 

 Mountain region, extending far north into the Canadian prov- 

 inces. Some quarries furnish a brown sandstone, much prized for 

 ornamental building ; but in general the rocks of this period are 

 not of much economic value. The rocks seem to have been 

 formed in shallow water, and the abundance of mud cracks, rain- 

 drop impressions, and tracks of animals show that the sediments 

 were often half-emerged sand flats. 



Jurassic rocks are found near the Black Hills, and in the 

 Uintah, Wasatch and Sierra Nevada mountains, usually sand- 

 stones, sandy limestones, etc. 



The cretaceous rocks are beds of sand, clay, shells, green sand, 

 limestone ; all these beds usually loose, easily crumbled, but occa- 

 sionally compact beds are found. They occur in detached areas 

 along the Atlantic and the Gulf coasts, and north along the 

 Mississippi almost to the Ohio river; along the slopes of the 

 Rocky Mountains from Texas into Canadian territory quite to 

 the Arctic ocean, the thickest beds being in Colorado, Utah, and 

 Wyoming, where the rocks are fully 9,000 feet thick. The life 

 forms were abundant. Among plants there were equisetae, ferns, 

 conifers, and others known during the coal period. The cycads, 

 having the appearance of palms, with leaves that unrolled like 

 ferns and wood like the pine, were characteristic and peculiar. In 

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