270 REPORT OF THE AMERICAN COMJklTTEE. 
stratigraphy of tlie Tertiary beds of Alabama will perhaps form 
the best introduction to the subject. 
EOCENE. 
The Tertiary beds of Alabama thus far known have been con- 
sidered as Eocene, and their subdivisions are as follows : 
f Upper, White Limestone, 3-50 feet. 
! ,,. ,„ /Claiborne, 150 " 
Eocene, i Middle, 1 ,, , ' „„„ „ 
' <- Buhrstone, 300 
[ Lower, Lignitic, 900 to 1000 " 
Along the Tombigbee and Alabama rivers we find directly 
overlying the sandy and calcareous beds that form the upper- 
most of the undoubtedly Cretaceous deposits, known as Ripley, 
first, a crystalline limestone, then an impure argillaceous lime- 
stone, both bearing a decidedly Cretaceous aspect, but, according 
to the determinations of Mr. L. C. Johnson, containing fossils 
which are undoubtedly Tertiary. These beds increase very 
greatly in thickness towards the eastern part of the State. 
Above these limestones are seen about 100 feet of black clays 
passing upwards into a great mass, 800 feet or more, of grayish 
cross-bedded sands interstratified with thin sheets of gray clay 
and occasional beds of lignite, and, at seven or eight horizons, 
holding beds containing marine fossils. The black clays which 
lie at the base of this division form the substratum of what 
Hilgard has called " the Flatwoods," and they correspond in the 
main with Safford's Porter's Creek group in Tennessee. 
The rest of this series above the black clays has been called, by 
Dr. E. W. Hilgard, the Lignitic — (Professor Heilprin has sug- 
gested the name Eolignitic), — and it has a thickness along the two 
rivers of 800 to 900 feet. The fossils of the seven marine beds 
above alluded to have been recently studied by Mr. T. H. 
Aldrich of the Alabama Geological Survey. 
Westward in Mississippi, according to the investigations of 
Mr. L. C. Johnson, the lower beds appear to thin out and their 
place to be taken by a lignitic phase of the Siliceous Claiborne of 
Hilgard. In eastern Alabama and Georgia, also, these lower 
lignitic beds appear to thin out, while the interstratified marine 
shell beds become more prominent. 
While holding many fossils identical with those of the next 
