CLINTON CONGLOMERATES AND WAVE MARKs. 191 
composed, locally, of rolled pebbles of the Waterlime. Many 
floated fragments of land plants, including branches of Lepido- 
dendra, have been found in the Corniferous at Delaware and 
Sandusky, showing the proximity of land. ‘1 
Fiillsboro Sandstone of Highland county.—Professor Orton, in 
the 1870 report, page 283, wrote: ‘‘The only remaining division 
of this extensive series (Niagara) of rocks is the Hillsboro sand- 
stone, the sixth member of the Niagara group in Highland 
county. . . . It is a unique and original contribution of High- 
land county to the general geological scale. Limestones and 
calcareous shales constitute the only kind of rocks that have 
been referred to this period hitherto, in the Mississippi Valley ; 
but at Fiillsboro and on the eastern border of the county generally, a 
siliceous sandstone of a good degree of purity is found termin- 
ainem ue Segliesa uw) o8..) (hie thicknessvor this sandstones at 
Lilley’s Hill (at Hillsboro) is 30 feet, and no greater thickness 
is shown elsewhere. The sand that makes up the rock is fine- 
grained and but slightly cemented.” 
GENERAL CONCLUSIONS. 
A brief résumé of the more important facts regarding the geograph- 
cal distribution of wave marks and pebbles—I\n the Trenton of 
Kentucky the wave marks and pebbles are mentioned only from 
the southeastern counties of the Blue Grass region, Garrard, 
Clark and Montgomery. The pebbles occur near the top. 
” 
In the Utica or ‘‘Lower Hudson,” rounded limestone pebbles 
occur in the lowest bed in Washington county, and apparently 
also in Mercer, Boyle, Clark and Montgomery counties. These 
are again the southern counties, and lie in about the same set as 
those mentioned as containing pebbles in the Trenton. The 
occurrence of pebbles at West Covington, opposite Cincinnati, 
and the widespread distribution of wave marks wherever the 
upper strata of the Lower Hudson are exposed (the list of coun- 
ties completely encircling the Blue Grass region of Kentucky ) 
point to a more widespread exposure to wave action. 
In the Middle Hudson wave marks are mentioned from near 
