332 E. O. ULRICII REVISION OF THE PALEOZOIC SYSTEMS 



As will be shown in a later section, the Cambrian submergence was in- 

 terrupted by movements at the close of the lower Cambrian and again at 

 the close of the middle series. Later the waters of the succeeding late 

 Cambrian (Saint Croix) invasion apparently were completely withdrawn 

 from the North American continent at the close of Cambrian deposition* 

 The frequently asserted continuity of sedimentation in continental basins 

 from the Cambrian into the Ozarkian (including Saratogan), or Beek- 

 mantown, or Ordovician, or whatever the next succeeding deposits may 

 have been called, in reality did not occur. The supposed transition is 

 based on mistaken correlations of Ozarkian rocks in New York, and more 

 especially in the deep Appalachian and Cordilleran troughs, with older 

 deposits in the Mississippi Valley, Oklahoma, Texas, and the Rocky 

 Mountains, that I regard as representing the closing stage of the first 

 Paleozoic system in America — in other words, of the American Cambrian 

 system as defined in this work. 



The fossiliferous Ozarkian, so far as I can learn, begins everywhere in 

 America with the first introduction of the typical Dikelocephalus fauna. 

 Of course, the immediate ancestors of this trilobite lived before, but their 

 remains seem not to occur in accessible deposits, being apparently absent 

 and probably later than the youngest of the beds referred to the revised 

 Cambrian. In the Mississippi Valley typical representatives of the genus 

 are accompanied by a well developed molluscan fauna that before the 

 close of the middle Ozarkian series (Saratogan) spread widely in America. 

 Wherever I have had an opportunity to study the beds there was never 

 any trouble to find evidence of an hiatus between the Ozarkian and the 

 underlying upper Cambrian when this was present, and the final deposits 

 of the latter always exhibited criteria of extensive shoaling and subse- 

 quent emergence. 



The widely effective Saratogan submergence, with which Ozarkian 

 deposition began in New York, affords excellent examples of overlaps. 

 The deposits of this second series of the Ozarkian are rather well devel- 

 oped in the Champlain Valley but thin rapidly northward by overlap in 

 Canada. They overlapped also all around the Adirondack island, though 

 tilting of this dome is indicated about the middle of Saratogan time that 

 prevented deposition on the western and northern flanks during the later 

 (Little Falls dolomite) half of the epoch. The great Knox dolomite, the 

 larger part, if not the whole of which, as developed in Copper Ridge and 

 at Knoxville, Tennessee, represents the New York Saratogan in the south- 

 ern Appalachian region, likewise overlaps northwardly to extinction in 

 the western folds of the great valley. In the most western of these it ex- 

 tends as far north as Martinsburg, Pennsylvania. In another, more east- 



