K /Suess — Paleogeogra/phy of North America. 105 



other information will be found in the last volume, which was 

 not at your disposal. I will restrict my remarks to the undis- 

 turbed region extending to Texas and the western mountains. 



These undisturbed regions (those in which Cambrian is not 

 folded) not only show the clearest marks of the negative peri- 

 ods, but also the slow creeping upon them of the transgressions. 

 The negative marks of the strand-line are found more rarely 

 and with difficulty in the folded regions with their rich marine 

 series. 



A great negative phase appears at the limit of Jurassic and 

 Cretaceous (Comanchic). This is the Weaklen, extending cer- 

 tainly from Poland across hi an over, southern England, Spain, 

 Portland, to the Potomac beds of Mainland, Texas, and Colo- 

 rado to Alberta, etc. If no other case were known, this one 

 would be sufficient to prove the wide extension of similar 

 movements. The contrast is given by the Spiti beds of the 

 Himalayas, as described a short time ago. In England the 

 Jurassic ends with oscillations in the Purbeck, then follows 

 the Wealden as the time-equivalent of lower Neocomian 

 (Berriasien) and then the marine Cretaceous series. In Hima- 

 laya all is marine and difficulties exist in separating the latest 

 Jurassic (upper Tithonian) from the Berriasien. At this time 

 climatic differences seem to have existed in the seas (Knox- 

 ville?).' 



1 do not think that lower Neocomian exists in Texas ; the 

 oldest forms from Trinity seem to me to be Gault, according 

 to Kalian's determination, and although it may seem daring on 

 my part, I venture to state that the equivalents of the Euro- 

 pean Cenomanian (upper Greensand) begin Avithin the Freder- 

 icksburg. This is the introduction to the great transgression 

 known to me (your Coloradoan Sea is a part of it). The full 

 series exists with lower Neocomian in the southern Andes as 

 well as in the Alps, but in leaving these one sees the Gault 

 creeping over older rocks in northern France while the Ceno- 

 manian transgression spreads from the United States through 

 Europe, covering the Sahara from the Atlantic to the Nile, 

 then passing southern Russia and attaining even the desert 

 near Kashgar. Then there seems to appear a pause or even 

 a small regression during the Turonian, perhaps coinciding 

 with your remarks about Pierre, and after this the maximum 

 of the transgression is attained in the Senonian with outliers 

 in the Arctic (central western Greenland) as well as in the 

 Antarctic (Scott). 



Next appears the great and probably rapid negative move- 

 ment of the strand-line, which forms the limit between the 

 Mesozoic and Cenozoic. North America indeed possesses 

 extremely little lower Eocene. This absence seems to occur 



