Outcropping rocks range as low as the Stones River and include the High Bridge, Lexington, and Cynthiana beds. Their general character, significant fossils, and stratigraphic relationships are outlined. Two wells have penetrated the Cambrian, one probably the pre-Cambrian. Contributions by several workers have modified hitherto accepted stratigraphic alignments.

1. The upper Camp Nelson has been referred to the Lowville, and the Tyrone, and probably the Oregon along with it, to the Trenton.

2. The Perryville is shown to be a facies of the upper Benson. The so-called Perryville of Franklin and Woodford counties, renamed the Devil's Hollow division of the upper Lexington, is regarded as a facies of the upper Woodburn and probably also the lowermost Cynthiana.

3. The Sulfur Well member (pre-Greendale) of the lower Cynthiana in the southern and southwestern Bluegrass has been shown to be an overlapping facies of the late Lexington. Such a relationship also exists on the east.

4. The Lexington-Cynthiana-Eden is probably a conformable succession. Previously recognized mid-Ordovician structures, based on unconformable overlap, are abandoned as the overlap is shown to be one of facies.