LYON—ROCKS OF KENTUCKY. 615 
a. For the details of the mass of a, see Reports of the Ge- 
ological Survey of Kentucky. 
b. Fifth Sandstone above the base of the Millstone Grit Divis- 
ton.—This mass is usually a coarse brown sandstone, some- 
times containing beds of conglomerate from four to six feet 
thick, the surfaces of the different beds being sometimes 
thickly strewn with pebbles; again, large districts of country 
may be observed where this is the surface rock, and nota 
single pebble can be obtained derived from it. It is also 
subject to great variations in thickness even in short dis- 
tances, the whole mass running sometimes as low as forty, and 
again thickening up to two hundred feet, and even above the 
ast figures. 
¢. Fourth Limestone intercalated in the Sandstones of the Mil- 
stone Grit Series —This mass is generally composed of thin- 
bedded limestones; not unfrequently some thick beds occur 
near the top of it; these thick beds are generally found to 
contain great numbers of an undetermined Belero, hon(?). 
The mass of ¢ is also subject to great modifications oth as 
to the thickness and the character of the materials ; in fact, the 
limestone disappears entirely, and the place of the bed is 0¢- 
cupied by aluminous shale, or every conceivable modification 
of limestone, and earth limestone, interstatified’ with mars 
and thin-bedded clay shale, replaces it. In some districts it is 
entirely absent, the mass of & resting on beds below it. 
d. The mass of d is a local bed, and is not so regularly per- 
Srey ; again, yellow, blue, yellow; grey, red, ete. ; in different 
bands, in the order situa domiond to five feet e mgs 
a 
fe bse 
¢. Fourth Sandstone, ‘Millstone Grit Series. — This 1s —_ 
Temarkable bed, and a good horizon ; when present It 18 alv 
shell olor, and always contains the remains 
eu, the internal casts or the vacant spaces W 
