NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 29 



classed as stinkstone. These carry a large and characteristic fauna. They are in 

 turn overlaid by clays and less fossiliferous limestones and shales. The limestones 

 become less fossiliferous toward 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 interstratified with sandy shales. There are also beds of white, red, and 

 spotted sandstones. Toward the top of the beds they 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 is found in 

 the Wichita beds. The red clay contains vertebrate fossils, the bluish clay has 

 copper, and the limestones have large quantities of invertebrate fossils. 



"The fossils mentioned by Dr. White in his article heretofore quoted, published 

 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 Meso- 

 zoic types, and some that are characteristic and peculiar to the Permian. It will 

 be seen from the list that the broad-shouldered Brachipods, which were so abun- 

 dant in the Coal Measures, are wanting." 



"These Clear Fork Beds* are composed of limestones, clay and shale beds, 

 and sandstones. 



"The limestones are mostly magnesian and carbonaceous, some of them being 

 so largely impregnated with carbonaceous matter that when struck with a hammer 

 they give off a peculiar odor, which has given such stones the name of 'stinkstone.' 

 These limestones carry an abundant and characteristic fauna. 



"The sandstones are not so abundant as in the Wichita Beds, and are not so 

 massive, but are generally thin-bedded. 



"The clays are blue and red, the red occurring in thick, heavy beds. The blue 

 clays are in places copper-bearing. The conglomerate is similar to that found in 

 the Wichita Beds, but is not so abundant, and is less compact. 



"Toward the top the sandstones become more shaly, and the clays more sandy. 

 There are also some beds of gypsum, but not in such abundance as is found in the 

 Double Mountain Beds." 



Gordon's first account of Clear Fork formation is included in his de- 

 scription of the Wichita formation, page lo. A more recent and more com- 

 plete account by Gordon ** appeared in 19 13: 



"Overlying the Wichita formation conformably are red and blue clays, sandy 

 shales, and sandstones, including deposits of g>'psum and a few beds of earthy 

 magnesian limestone. These rocks were subdivided by Cummins into the Clear 

 Fork and Double Mountain beds, but, as stated by that author, 'no attempt has 

 been made to determine a definite line of division between the two,' and in view 

 of the character of the sediments, it is evident that the determination of such a line, 

 if it can be made at all, will require much detailed work. Hill proposed the term 

 Brazos series to embrace 'all those rocks of Texas, Oklahoma, Kansas, and New 

 Mexico between the top of the conformable Coleman division of the Carboniferous 

 beds below (and) the base of the unconformable Cretaceous above,' but the sug- 

 gestion has not been elsewhere adopted. According to Gould, these beds corre- 

 spond to those in Oklahoma which he has termed, in ascending order, the Enid, 

 Blaine, Woodward, Greer, and Quartermaster formations. 



» Cummins, Second Annual Report, Texas Geological Survey, i8qo, p. 401. 



'' Gordon, U. S. Geological Survey, Water Supply and Irrigation Paper No. 317, pp. 28, 29, 1913. 

 3 



