188 PERMIAN OF TEXAS AND ITS OVERLYING BEDS. 



cretions, ranging in size from one-quarter of an inch to several feet in diame- 

 ter. The sandstones are often shaly in structure, while in other places they 

 are massive. They are often ripple-marked and at other places have a cross- 

 bedded structure. The concretions are very hard, and retain the peculiar 

 structure of the sandstone in which they occur. The clays are red and 

 bluish. In the red clays are nodular masses of clay, iron, and lime, which 

 often take the form of geodes, filled with tabular lime-spar in the center. 

 The bluish clay is copper -bearing in many places. The conglomerate is 

 composed of rounded pieces of clay or clay ironstone, cemented together 

 by iron. Fossils occur in all these beds, which consist mostly of plants and 

 vertebrates, very few invertebrates being found. The largest number of the 

 vertebrates described by Prof. E. D. Cope were taken from the Wichita Beds. 



THE CLEAR FORK BEDS. 



The Clear Fork or Middle Beds of the Permian are composed first of 

 bedded limestone, magnesian, and earthy, which are sometimes carbona- 

 ceous enough to be classed as stink stone. These carry a large and char- 

 acteristic fauna. They are in turn over] aid by clays and less fossiliferous 

 limestones and shales. The limestones become less fossiliferous towards 

 the top of the beds. The clays are both red and blue, the former color 

 largely predominating. The red clays are in thick beds and are in places in- 

 terstratified with sandy shales. There are also beds of white, red, and 

 spotted sandstones. Toward the top the beds become more sandy, and a few 

 seams of gypsum occur, but not in the quantity in which it is found in the 

 Double Mountain Beds. There is also the peculiar kind of conglomerate 

 which has been described in the Wichita Beds. The red clays contain verte- 

 brate fossils, the bluish clay has copper, and the limestones have large quanti- 

 ties of invertebrate fossils. 



The fossils mentioned by Dr. White in his article heretofore quoted, pub- 

 lished in the American Naturalist, were taken principally from the Clear 

 Fork Beds. By reference to the list it will be seen that it embraces both 

 paleozoic and mesozoic types, and some that are peculiar to and characteristic 

 of the Permian. It will be seen from the list that the broad shouldered 

 Brachiopods, which were so abundant in the coal measures, are wanting. 



THE DOUBLE MOUNTAIN BEDS. 



The Double Mountain or Upper Beds of the Permian are composed of 

 sandstones, sandy shales, limestones, red and bluish clays, and thick beds 

 of gypsum. The limestones are quite earthy, and are often very full of 

 the casts of fossils, the newer types largely predominating. The shales are 



