170 THE JOURNAL OF GEOLOGY. 
PEBBLES AND WAVE MARKS IN THE ONEIDA, MEDINA, AND 
CLINTON GROUPS. 
The Medina of Ohio and Kentucky furnishes so few facts of 
interest in this connection, and in places so difficult to distinguish 
from the Clinton, that it will not be considered separately but 
will be discussed under the above heading. 
Observations of the Kentucky Survey.—No Oneida is exposed 
in Ohio. In Kentucky a conglomerate two inches thick, with the 
characters ascribed to the Oneida conglomerate of New York, is 
found in Boyle county. 
Medina.—The rock supposed by Kentucky geologists to 
belong to the Medina is exposed in Lincoln county. Here it 
reaches a maximum thickness of 35 feet. In the western part 
of the county it is thinner. The whole series has the appearance 
of having been deposited largely or entirely by currents, and 
sometimes, probably, in the face of waves, as at several points 
one or two layers have a wave-like structure. In Garrard county 
the Medina has a maximum thickness of 35 feet, decreasing 
towards Madison county, northeastward. In Clark county the 
total thickness of the Medina is probably 20 feet, including nine 
feet of sandstones and shales at the bottom, and 11 feet of lime- 
stones and shales at the top. Eastward, in Montgomery county, 
these shales increase in thickness. Only 10 feet are accredited 
to the Medina in Bath, while 20 feet are given for Fleming 
county, and the same thickness, 20 feet, also for Mason county. 
The Medina in Marion county measures only 14 feet. In 
Washington county it seems to occur with a thickness of 30 feet 
in one case, but another section gives 14 feet. In Nelson it 
varies from three to 20 feet. In Oldham county it varies from 
10 to 30 feet. 
Taking into consideration only the area between Marion 
and Bath counties, the Medina seems to thicken towards the 
southeast. Between Washington and Oldham counties its thick- 
ness is very variable, and in Fleming and Mason counties the 
thickness is apparently greater than in Bath on the south, and 
certainly surpasses that of known exposures in Ohio. Wave 
