AGE OF REPTILES. 237 



The term Oolitic is sometimes applied to it, though com; 

 monly it is confined to one portion only of the Jurassic 

 period, in which one of the limestones formed is oolitic 

 in its structure. The term Cretaceous, from the Latin 

 word creta, chalk, is applied to the closing period of the 

 Reptilian age, because the chalk of England and Europe 

 is one of the rocks of the system belonging to that pe- 

 riod. In this country we have the system, but the chalk, 

 which is so prominent in those countries, is left out here. 



340. Triassic Rocks. The rocks of this period are 

 mostly sandstones, shales, conglomerates, and sometimes 

 some limestones. So prominent are the red sandstones 

 that the whole system is called the New Red Sandstone, 

 in distinction from the Old Red Sandstone of the Devo- 

 nian age. In the valley of the Connecticut the material 

 for the rocks of this formation was derived from the 

 crystalline rocks in the neighborhood, chiefly by the ero- 

 sive action of water. The freestone of Connecticut and 

 New Jersey, so much used in building, comes from this 

 formation. In the western part of this country the Tri- 

 assic rocks are sandstones and marls of a brick-red color, 

 often having gypsum in them. The red color, so preva- 

 lent in the sandstones, though varying much in shade, is 

 owing to the presence of oxyd of iron. The life-record in 

 the rocks of this formation is scanty, because they are 

 not well suited to the preservation of fossils. 



341. Localities. In the eastern part of this country 

 the Triassic rocks are surface rocks along between the 

 Appalachians and the Atlantic coast. In the Connecti- 

 cut Valley they extend from the Sound at New Haven 

 up to the northern part of Massachusetts. There stand 

 up in the midst of them Mount Holyoke, Mount Tom, 

 East and West Rock, and other Trappean elevations, 

 imparting variety and grandeur to the scenery. In the 

 West this system is extensively spread over part of the 

 slopes of the Rocky Mountains. The Triassic system is 

 developed in various parts of Europe and in England. 



