104 E. Sxiess — Paleogeography of North America. 



cides very nearly with what yon say about the fixing of the 

 broader relations by the Appalachian Revolution of the Atlan- 

 tic realm. Only sinking of regions seems to have occurred 

 since that time in northern Europe. 



8. Comparison of several great eustatie movements. 



It has long been known that the stratigraphic series of the 

 Alps is more complete by far than that of its foreland. Within 

 this foreland the pre-Permian mountains (which I compare 

 to your Appalachians) are to be separated from those regions 

 in which no orogenetic process is known since the beginning 

 of the Cambrian. Such I once named Archeboles, but the 

 name is bad, because pre-Cambrian folds are well known in 

 these same regions. The environs of Saint Petersburg and the 

 rim of the Baltic shield are types of horizontal Cambrian. 



This difference between the less extensive marine series of 

 the foreland and the more complete series of the folded chains 

 seems to exist all over the world with few exceptions (south- 

 eastern Himalaya where the fore-depth cuts off part of the 

 foreland, Mackenzie district and Argentina where the folds 

 enter the less complete series of the foreland, the Jura Moun- 

 tains which form a sort of complicated parma with a transi- 

 tional series). In seeking to compare the marine series of the 

 United States with that of Europe, I believe I ought to divide 

 the immense array of facts offered by your maps into three 

 groups or regions, as defined by Dana in 1859, viz., (1) the so 

 called Azoic nucleus or Laurentia, (2) the Appalachians and 

 (3) the western mountains. To these I add as a fourth area 

 the United States Range of Ellesmere land which is thrust on 

 Laurentia from the north and adds a new example of the com- 

 pletion of the marine series as soon as a folded region is 

 entered. 



Of these four regions Laurentia presents the imperfect ma- 

 rine series of an undisturbed nucleus or shield and has much 

 in common with Gondwana land ; Appalachia may be regarded 

 as the continuation of the pre-Permian mountains of Eurasia 

 (AJtaides) ; the United States Range seems to be an Asiatic 

 fragment; while the Mesozoic and upper Palaeozoic of your 

 western mountains has decided relations to Tethys. In this 

 I believe I am not in contradiction with your results. 



Europe cannot boast of a Palaeozoic series comparable in 

 completeness with that of the United States. I have read 

 with great interest what you write regarding the interrelation 

 of Atlantic biota such as that of the Paradoxides fauna, but I 

 fear I am not able to say more about the older palaeozoics 

 than I have already said in my "Face of the Earth ;" perhaps 



