

across Mississippi, Louisiana, and Texas. 371 



VII. The southwestern or central Texas end of the Appa- 

 lachian land area was formerly covered by Cretaceous sedi- 

 ments, but it has since been uncovered by erosion ; further 

 east it is still concealed. 



VIII. The Carboniferous beds uncovered in Texas all belong 

 to the Upper Coal Measures ; it is inferred that a greater thick- 

 ness is still covered. 



IX. The character of both the Silurian and Lower Coal 

 Measures sediments of the Ouachita uplift show that they 

 came from the south, so that the land area must have been in 

 that direction during Paleozoic times. 



X. The sea occasionally invaded both the Arkansas and 

 Texas synclinal troughs during Coal Measures times, but coal- 

 forming conditions obtained in the Texas syncline later than in 

 the Arkansas basin. 



XI. The Tertiary depression was probably more marked on 

 the Arkansas than on the Tennessee side of the em bay men t ; 

 this is shown by the Cretaceous border being concealed by the 

 Tertiary deposits in Arkansas, while in Tennessee, Mississippi 

 and Alabama they are exposed in a broad belt. 



