698 A. F. FOERSTE 



rian deposits of the geosyncline differ sufificiently from those of 

 the geanticline to form a distinct province. The Silurian deposits 

 of the geosyncline extended northward into southern Illinois and 

 the adjacent part of Missouri. The formation of this geosyncline 

 was the first expression of the series of changes which finally 

 resulted in the formation of the lower Mississippi valley. 



Mesodevonic limestones are but scantily represented in the 

 Tennessee River valley. At the Whirl in the Buffalo River, 4 

 miles north of Bakerville, they are 3 feet thick. Forty-five miles 

 farther east, along the Harpeth River, they vary in thickness 

 between 3 and 12 feet. At both localities, the Mesodevonic 

 limestones belong to the Onondaga horizon. At Newsom, the 

 Onondaga limestones rests on the equivalent of the Lego bed; at 

 Pegram, on the lower part of the Brownsport bed; and north of 

 Bakerville, on the Camden chert bed. The unconformity thus 

 indicated suggests the existence of the Cincinnati geanticline in 

 times preceding the Mesodevonic. 



The Paleodevonic is absent along the western flank of the 

 Cincinnati geanticline, in Tennessee, Kentucky, and southern 

 Indiana. It is exposed, however, at numerous points in the 

 Tennessee River valley, especially west of the Tennessee River. 

 Both the Oriskanian and the Helderbergian are represented. 

 Where more fully developed, the passage from the Helderbergian 

 to the Oriskanian appears to be gradual, not indicating any 

 unconformity between them. At their attenuated margins near 

 Linden, the line of demarkation between the beds is very dis- 

 tinct. This suggests the growth of the Cincinnati geanticline 

 during the Paleodevonic times. 



Very few localities have so far been discovered where the 

 contact between the Helderbergian and the Silurian may be 

 studied. At all of these localities the Linden bed rests upon the 

 Brownsport bed, and the change from the Silurian to the Devo- 

 nian fauna is abrupt. It is impossible to determine at present 

 whether the Linden bed rests upon higher horizons of the 

 Bro\^nsport bed westward than along the eastern line of outcrop. 

 The faunus of the Brownsport have not yet been studied in 

 sufificient detail to warrant any conclusions at present. If the 



