314 Postscript. 
“5th. The age of the nummulite limestone of Alabactile seems to 
have been involved in considerable obscurity, it having been commonly 
referred to the secondary period, or considered as an upper cretaceous 
formation, or as possibly intermediate in age between the tertiary and 
secondary strata. After visiting the neighborhood of Suggsville, Ma- 
con, and Clarksville, Ala., lam persuaded that it is a tertiary limestone 
newer than all the beds of the well known Claiborne bluff, and ying 
immediately above the calcareous rock in which the Zeuglodon occurs. 
It is therefore by no means in the lowest part of the Eocene system Pe 
the South. Hitherto I have always met with it in hills considera 
higher above the sea, than the top of the bluff at Claiborne, a circum- 
stance which, in a region where the stratification is horizontal, would 
imply a newer deposit, even if the sections near Suggsville and Clarks- 
ville, showing actual superposition, had been less satisfactory. I did 
not meet with the limestone in question in the bluff at Claiborne, which 
I have no doubt is owing to the fact that the calcareous strata are cut 
off at the top, before they extend upwards into the nummulitic beds, 
“6th, The conclusion last stated, will make it necessary in future to 
omit from the list of cretaceous fossils, such species of shells as have 
been referred to the secondary formations, simply on the ground of their 
occurrence in the nummulitic limestone. The fossils which I met with 
most abundantly in the latter, were the Nummulites Mantelli, (Morton,) 
ahd Pecten Poulsoni. I also found in the lower part, Pecten perplanus, 
Ostrzea panda, and Plagiostoma dumosum, a large species of Cypraa, 
a Lunulite, and other corals. 
“7th, The shale of the tertiary white limestone country of Alabama, 
is covered, like that of the Savannah River in Georgia, with river deposits 
of red clay, with quartz gravel, fine yellow, white, and pink sands, white 
porcelain earth, and occasionally chert and clay with sand intermixed. — 
In many places i in Georgia, where the buhr-stone occurs in this series, 
I have found in it distinct casts of Eocene testacea and corals, and I 
have shown, in the Proceedings of the Geological Society of London, 
the manner of its superposition to the subjacent calcareous beds in 
Scriven County, Georgia, which is equally applicable at Claiborne and 3 
in Clarke County, Alabama. Whether this upper deposit in Alabama be 
Eocene, and identical in age with that of Georgia, as I suspect, lam 
unable as yet positively to prove by the evidence of organic remains, 
although I have met with some faint impressions of shells and silicified 
wood in Clarke County. 
“8th, The underlying Eocene or white limestone series, has a very 
undulating surface, on which the newer beds, many hundred feet thick, 
were deposited. The inequalities having been thus removed, and 
the hollows filled up, the existing valleys were excavated in n both de- 
