114 STUART WELLER 



more or less inclosed Appalachian Basin east of the Cincinnati island, 

 where the Maxville limestone represents the Ste. Genevieve formation 

 of the Mississippi Valley. To the southwest, in northern Arkansas, 

 the Spring Creek limestone, a formation which, with the Batesville 

 sandstone, is essentially contemporaneous with the Ste. Genevieve, 

 and probably uncomformable upon the subjacent Osage beds, carries 

 a most remarkable fauna with peculiar immigrant forms from the far 

 southwest,' a faunal character which indicates that the Mississippian 

 sea reached so far in that direction as to communicate with the Western 

 Continental Province, where these peculiar forms had existed, some 

 of them having persisted from Devonian time. 



Subsequent to the great extension of the sea during Ste. Genevieve 

 time the northern portion of the Mississippi Valley Basin became dry 

 land, and so remained until it was reoccupied by the sea in Pennsyl- 

 vanian time, with only a partial readvance in early Chester time. In 

 the extreme southern portion of Illinois and in Kentucky, Ulrich^ has 

 recognized three members in the Ste. Genevieve formation, the Fre- 

 donia, the Rosiclare, and the Ohara, but in all the region north of 

 Chester, III, the upper portion is wanting and the superjacent Cypress 

 sandstone rests unconformably upon the lower beds of the Ste. Gene- 

 vieve. The higher beds of the Ste. Genevieve in the extreme southern 

 Illinois, especially the Ohara beds of Ulrich, bear a fauna which has 

 much in common with the faunas of the Chester above the Cypress 

 sandstone, but even here there is possibly an unconformity between 

 these beds and the Cypress. 



The Cypress sandstone initiates the Chester, the closing epoch of 

 the Mississippian in the typical portion of the Mississippi Valley 

 Basin, during which period the conditions of sedimentation were 

 continually shifting, there being interbedded Hmestone, shale, and 

 sandstone formations, the limestone and shale predominating below, 

 above the initial Cypress sandstone, and the sandstones being more 

 conspicuous above. No remnant of these beds is preserved, so far as 

 known, north of a point some miles south of St. Louis, although it is 

 possible that the Chester sea extended further north than this. It is 

 quite certain, however, that this sea never had the great extent to the 



1 Williams, Am. Jour. Set. (3), XLIX, 94-101. 



2 Professional Paper, U. S. G. S., No. 36, p. 38. 



