THE ARKANSAS COAL MEASURES. 1 97 



Carboniferous age, from Shinall mountain. In quarries in the 

 sandstones of Big Rock, near the city of Little Rock, are found 

 plant remains of indeterminable character. The stratigraphy of 

 the Survey places both localities in the Lower Coal Measures, 

 and probably above the fossiliferous sandstones of Bee Rock, on 

 Little Red river. 



THE PACIFIC CARBONIFEROUS SEA. 



Revoliitio7i in Devo7iian time. — In Paleozoic times there have 

 been many revolutions and alternations of continents and seas, 

 and consequent readjustment of their inhabitants to new sur- 

 roundings. One of the greatest of these was that which broke 

 up a large zoological province, and put in direct connection 

 regions that before were separated. 



Dr. A. Ulrich ' has shown that in lower and middle Devonian 

 the faunas of Bolivia, Brazil, the Falkland Islands, and South 

 Africa were very similar to those of North America, and that 

 they were very different from the faunas of Europe and Asia. 

 This state lasted until the end of the middle Devonian, when 

 the revolution began. Professor H. S. Williams^ has shown that 

 with the beginning of the upper Devonian in America there 

 came in a fauna, many species of which were not the direct 

 descendants of those immediately preceding them. This new 

 fauna was, however, closely related to forms known in Europe 

 and Asia, but unlike those of the southern regions. 



Professor Williams 3 afterwards elaborated this theory, and 

 followed out closely the changes that were inaugurated towards 

 the end of the Devonian. The culmination of these changes 

 produced the Pacific Carboniferous sea. 



The Carboniferous sea. — From chapter V., in Suess' " Antlitz 

 der Erde," Vol. II., we get many valuable suggestions as to the 

 outlines of the Pacific Carboniferous ocean. The Subcarbonifer- 



'Beitrage zur Geologic und Palaontologie von Siidamerika, I., " Palaozoische 

 Versteinerungen aus Bolivien." 



^ Bull. Geol. Soc. America, Vol. I., " The Cuboides Zone and Its Fauna. 



3 Proc. Amer. Assoc. Adv. Sc, 1892, Section E, Address, " The Scope of Paleon- 

 tology and Its Value to Geologists." 



