GEOLOGY OF THE LOWER AMAZON REGION 741 



prolific coral faunas so abundantly developed about Louisville, 

 Kentucky. 



The reason why the Lower Devonic faunas of northern Europe, 

 North America, and South America have so much that closely binds 

 them together is because the oceans of these areas were in communi- 

 cation. This is strikingly shown in the great pelecypod development 

 of the Coblenzian of the Rhine region — genera upon genera almost 

 unknown in the Oriskanian making their first appearance in some 

 force in the Onondaga, and being in full development in the Hamilton. 

 The Coblenzian pelecypod development in Europe is very largely 

 wiped out or changed by the great Euro- Asiatic invasian coming in 

 just above the Spirifer cuUrijugatus fauna, which is known as the 

 Calceola fauna holding the horizon of the Onondaga in this country. 

 This fauna continues without very great change into the Stringo- 

 cephalus fauna holding the horizon of the Hamilton. While this great 

 invasion of Middle Devonic Euro-Asiatic faunas was proceeding 

 normally in Europe, the North American Middle Devonic had but 

 little connection with that region, and the fauna of a lower Devonic 

 fades was continued to the end of Hamilton time, when another great 

 physical change occurred, and northern Europe and America were 

 once more in communication. 



CARBONIC 



The marine Carbonic of the Lower Amazonas is divisible into two 

 divisions — a lower consisting essentially of sandstone, and an upper 

 of Hmestone. Of each division about 10™ thickness is known. The 

 limestone is locally very rich in well-preserved, often silicious fossils, 

 and these indicate that it is of Permo- Carbonic age . The sandstone 

 is devoid of fossils and of coal-beds, and, further, as the stratigraphic 

 relation to the limestone is nowhere clearly shown, its actual age 

 remains undetermined. The best exposures are those of the Tapajos. 

 Beneath the sandstone is a series of shales and shaly sandstone — the 

 Curua group of Derby, and referred by him and Clarke to the Devonic 

 (see statement under Devonic), but provisionally referred by Katzer 

 to the Carbonic. 



During the time of limestone deposition there were effusions of 



