122 NEW YORK STATE MUSEUM 



larger rivers and their barachois. There is probably no other region 

 where so ancient a topography is still in so obvious control. 



The southward spread of the sand transgression. Of the lime 

 seas of the opening Devonic in regions which bounded the broken 

 Siluric lands of northern South America, we have no knowledge. 

 The basin of the Amazonas is sheeted with Devonic sands that lie 

 close upon the Siluric limestones. The sand deposits of the Rios 

 Maecuru, Erere and Curua are not far away from the Siluric lime- 

 stones of the Rio Tapajos, and nowhere do we know aught of the 

 lime sediments which represented the deeper deposits of these 

 marine waters. They are absent or lie buried ; probably the latter, 

 for the sands are without evidence of continental character. The 

 Maecuru sandstones are sufficiently abundant in species to indicate 

 their part in the great sand transgression of the opening Devonic, 

 but the specific characters of this fauna are not such as to knit 

 them closely with Oriskany faunas of the northern continent. There 

 are the differences which have resulted from distance, from divid- 

 ing land and submarine barriers, from isolated evolution in embay- 

 ments or basin seas ; there are still the occasional indentities of 

 species, more often of distinctive genera, and, all told, in the 

 Maecuru sandstone an evident relationship in kind and time to the 

 Oriskany-Onondaga of the north. To the German geologist, 

 schooled in the Devonic of his own country, they are " Coblentzian " 

 and have been so termed, with reason, by Doctor Katzer ; but they 

 are not adequately characterized by such a term; even less so than 

 by the terms of the North American succession. 



From this Amazonas basin northward, Professor Schuchert 

 would disperse the fauna into North America by way of the Gulf 

 of Mexico embayment to connect with the Camden chert Oriskany 

 of Georgia. My own impression is that both the Maecuru and the 

 Camden " Oriskany " sediments represent, by their faunas, embay- 

 ments from a continental strand line which had connection with the 

 north by way of the Appalachian channel seas, or perhaps, with 

 even more probability, with an outer shelf strand now submerged 

 with so much of the eastern-shore Appalachia. 



We have recent knowledge of an extension westward of the 

 " normal " Oriskany fauna of New York into a pure white lime- 

 stone in St Genevieve county, Missouri, beneath it lying a well- 

 defined Helderberg fauna. This discovery carries the distribution 

 of the ( >riskany farther in this direction than was before known. 

 Thence lo the Camden cherts of Georgia is a distance st) short as 

 lo make, to express il in terms of paleogeography, bul a narrow 



