- OF SOUTH CAROLINA. 143 
laced filiments, that resemble a spider’s web, spread over the surface. The cavities in the rock have 
a vitreous appearance, as if it had undergone a partial fusion, and brown and striped jaspers are quite 
common in the mass. The lower part consists of a bed of Ostrea longirostris, in the form of 
casts, perforated by boring shells, which have left behind them casts, with the tubes and all beau- 
tifully preserved. Itis remarkable that when these rocks are decomposed, the substance left resem- 
bles silicate of alumina or porcelain clay. Indeed the passage of this substance into the silicified 
rock, may be distinctly traced. Among the fossils casts of corals are conspicuous, and I found 
what I suppose to be the Palmula, of Lea. a 
This is undoubtedly the most extensive locality of buhr-millstone in the State. Taken together, 
the beds exceed thirty feet i in thickness. 
Superimposed upon this, there is generally a stratum of fine sand, which overspreads almost the 
entire surface across the State, north of the calcareous beds of the Charleston Basin. On the crest 
of the sand-hills of this region there are often irregular beds of oxide of iron and sand, as I have 
already mentioned, when describing the denudation of Chesterfield District. In the vicinity of 
Aiken the seare conspicuous, as well as on the hills between that place and Graniteville. The beds 
are from three to six feet in thickness, but it was not before I reached Orangeburg that I discovered 
any fossils in them, There I had the pleasure of finding beautifully distinct casts of Cardita pla- 
nicosta, and in great numbers. This group of rocks, which constitutes, in South Carolina, as I 
shall presently show, the lowest beds of the Eocene, may be conveniently included under the name 
of Buhr-stone formation. 
The following section, from Aiken, down the “plane,” to Horse Creek, will place the relative posi- 
tion of these in a clear light. 
1.—Granite, on Horse Creek. 2.—Beds of sand-stone and grit. 3.—Beds of 
sand, gravel, colored clays, &c. showing false bedding. 4—Silicious clay 
bed. 5.—Silicified shells. 6.—Beds of sand and iron ore. 
A peculiar feature in the topography of this sand-hill region is the number of circular depressions 
that are scattered over the surface. They are not deep and conical, like “lime-sinks,” but flat and 
