, OF SOUTH CAROLINA. 159 
The next exposures towards the West occur on Cawecaw Swamp. At Pooser’s the marl is seen 
in the low ground, near the swamp, and a short distance above silicified shells are found. At Wan- 
namaker’s the marl was excavated for lime burning, and is overlaid by a bed of clay, containing 
casts of Lutraria lapidosa, Cardita planicosta, and Turretella Mortoni. This bed of clay is 
very remarkable: it is exceedingly light and porous; and it seems as if this character was the 
result of the solution and removal of the lime which it once contained in the form of minute par- 
ticles. I have seen hornstone, in the carboniferous limestone, assume the same appearance, from a 
similar cause. 
That the whole of this region is underlaid by marl there can be no doubt, for, besides lime sinks 
and other indications, it is laid bare in a canal, near the village, where I found perfect casts of Car- 
dita planicosta. The bed containing Lutraria lapidosa is found extending over a considerable 
space. It may be seen on the Columbia road, above the village, and again near Mr. McMaster’s, 
and at Poplar Springs, on the opposite side of the Edisto. On Limestone Creek I saw some indica- 
tions of the green sand bed, presented in irregular, indurated masses, mixed with clay. Below this 
the whole is covered up by more recent beds of sand and loam. 
I have already mentioned the upper edge of the marl, at Stroman’s, on S. Edisto, in which 
found ©. planicosta, partly silicified. Associated with these is a fine, compact marl stone, very 
rich in carbonate of lime. 
A mile or two above Binnaker’s bridge a poor marl occurs, forming a perpendicular bluff on the 
right bank of the river. The marl at the N. W. verge of the Charleston Basin differs very mate- 
rially from the Santee marls and marl stone, in the amount of carbonate of lime: the latter are 
every where exceedingly rich, whilst in the former clay and silica abound, and in some of the strata 
barely a trace of lime is found. This is the case with some of those on the Salkehatchie, near 
Brockton’s Ford, in Barnwell, where I saw sand carried out on the land, for marl, which had not a 
particle of marl in it, although it contained sharks’ teeth, and other indications of marl. 
Atacamp ground, near this place, I found some casts of shells, fishes’ teeth, and palatal bones 
of Diodon, which, together with some water-worn pieces of marl, were taken from a well. I 
searched this place diligently without finding any marl. Near the river a silicious rock occurs, 
containing a few fossils. 
Col. Graham pointed out to me a very interesting locality, on Lemon Swamp, where a rich white 
marl, with green sand above it, is found. Issuing from the marl are numerous clear and deep 
springs; but I could find no fossils. North of Barnwell Court House, about seven miles, on Buck 
Creek, I found a silicious marl, on the land of Mr. J. M. Whaley. It occurs at the bottom of a 
steep hill, near the stream. Marl is said to be exposed in several places, near the Court House; 
but I had no opportunity for further examination. 
On Tinker’s Creek there are several localities at which I found Eocene fossils, and among them 
the large Ostrea Georgiana, so abundant at Shell Bluff. Other exposures occur on the Lower 
Three Runs, but I was unable to find any mar! on the river bluffs. The characteristic fossil on 
the Savannah, and its tributaries, is O. Georgiana. 
The noted locality, Shell Bluff,* is on the right bank of the Savannah, and on the Georgia side :. 
* For a particular description of this bluff see Mr. Ruffin’s Report. 
