72 PROCEEDINGS OF THE NATIONAL MUSEUM vol.76 



In a mental review of the accomplishments in American strati- 

 graphy during the past 30 years the feature that impressed me more 

 than any other is that in this short time the aggregate thickness of 

 the Paleozoic rocks in America alone has been shown to be nearly 

 three times as great as we thought it in 1898. Many thick formations 

 that only 20 years ago were regarded as contemporaneous deposits 

 have one after another proA^ed to be of distinct ages; and when one 

 had been traced over or under the other the contact between them 

 still was broken; and when this contact had been traced to another 

 supposed equivalent the latter was found to wedge into the break 

 which opened often widely to receive it. However much our efforts 

 to fill the gaps have been rewarded we seem to succeed only in divid- 

 ing them into smaller breaks. And so, especially if views discussed 

 on preceding pages are not wholly visionary, I realize perhaps more 

 than any other that the task of building up the world sequence of 

 epicontinental marine deposits is far from completed. 



European geologists have not kept pace with us in recognizing 

 the extremely oscillatory nature of marine invasions and ensuing 

 deposition in epicontinental basins, nor have they discriminated and 

 correlated their Paleozoic formations in accord with anything like 

 our conception of small shallow seas that, in responding to frequent 

 surface warpings, were largely or entirely withdrawn or shifted from 

 one negative area to another. The older generation of geologists are 

 not expected to take very kindly to such unsettling views, but the 

 younger ones, in whose hands the future of the science lies, will, I am 

 sure, at least consider and try them out, because they promise a rich 

 reward. 



At present, detailed interprovincial stratigraphic correlations, re- 

 ferring particularly to lower and middle Paleozoic marine formations 

 on the two sides of the Atlantic, are shrouded in uncertainties. 

 These are occasioned partly by neglect of other than fossil testimony 

 but mainly by lack of strictly and specifically comparable faunal 

 evidence. When the generic aspects of such evidence seemed to point 

 toward a reasonable conclusion the hope of success, at least as regards 

 my own efforts, has been nearly always negatived by associated things 

 of contrary trend. I must, therefore, frankly confess that I do not 

 know how certain British formations and the usually smaller Scan- 

 dinavian and Baltic units will finally fit into the greater American 

 stratigraphic record, or how they will assist in the perhaps impossible 

 task of completing the geological time scale of the world. I fear, 

 too, that my present effort has succeeded rather more in complicating 

 the issues than in simplifying and deciding them. Let us hope that 

 it may prove the darkness that precedes the dawn. Time will tell, 

 for it will brinff the fuller and truer knowledge of the fossil faunas 



