178 GEOLOGICAL SURVEY 
On the swamps, between Black Creek and Lynch’s Creek, there are other exposures, but as they 
present nothing peculiar it is unnecessary to give a description. The highest point on the last 
mentioned creek at which marl is found, is a few miles above Dubose’s Ferry. On the left bank 
it occurs just at the water-line, in one or two places, and on the same side, a short distance inland. 
On the creek, the marl seemed to be composed principally of Chama congregata, but it was almost 
entirely under water. 
In the swamp, on the right bank of the river, I also found a rich bed, some feet below the surface. 
Between Effingham and Anderson’s Bridge the left bank of the creek is high, and exposes marl 
at several localities. At J. M. Timmons’s the Pliocene rises two or three feet above the water. A 
short distance from this it is seen again, at Elmore’s, and at the bridge it occurs, overlaid by heavy 
beds of sand and clay. A mile below, marl is again seen, which is the lowest point on the creek. 
Fossils are not numerous in these beds; but I saw a fine specimen of Carcharodon that was found 
at one of them. 
Between Lynch’s Creek and Black River a flat country intervenes, which precludes all know- 
ledge of the beds below. At Concord Church I found a bed of Pliocene marl, about four feet thick, 
which, like the Darlington deposits, rests upon the black shale. Others have been discovered in 
the vicinity, and on the opposite side of the creek, on the plantation of Dr. Muldrow, and on 
others adjoining, some exceedingly interesting beds have been found. In structure and composition, 
as well as in the very perfect state in which the fossils occur, they resemble the beds in the vicinity 
of Darlington Court House. 
I saw, from these, a portion of a tusk of a Mastodon. A very considerable quantity of marl had 
been carried out on the land at the time of my last visit to this interesting locality, so that I was 
enabled to collect and study the organic remains of the Sumter beds, with more than ordinary ease. 
As they present nothing to distinguish them from others, it is not necessary to enumerate the fossils 
in this place. 
South of the Brick Church Mr. McBride pointed out a locality on his plantation, in which all the 
fossil shells are converted into a mass of carbonate of lime, so that with the exception of Balanus 
proteus and Pecten eboreus, I could scarcely distinguish one. 
All the deposits here occur on the streams that flow into the river, but never in the river swamp. 
Generally the mar! is overlaid by a stratum of black mud, eighteen inches thick, in which, Mr. Mc- 
Bride informed me, he found the remains of marsh reeds, and boring crustacea. Superimposed 
upon this, is a bed of sand and clay, five to six feet in thickness. 
The next locality along the outer edge of the formation is found below Eutaw, in St. John’s 
Berkley, on the plantation of Mr. 'T. Porcher. Like the bed in Sumter, just described, it is com- 
posed of white, comminuted shells. The fossils that can be identified are barely sufficient to 
enable one to determine its age. 'They are Ostrea disparilis, Pecten septemnarius, Venus Riley?, 
and Fusus quadricostatus. 
This must be the locality “below the confluence of the Congaree and Wateree rivers,” whence 
fossils were sent by the late Stephen Elliott, Esq. from which Conrad inferred the existence of the 
Middle Tertiary in South Carolina. 
Like the rest of the principal Pliocene beds, when they are not exposed on the banks of streams, 
