PO BLEMGA TONS: 103 
origin—the Mobile Bay formation. Traced seaward this formation 
becomes continuous with the Biloxi, or at least with its lower part. 
The first, second, and third formations assigned to the Pleistocene 
in the above table, are therefore the fluviatile, estuarine and marine 
subdivisions of the same formation. 
Five to ten feet above the second bottom terraces, there is another 
series of sand terraces (No. 4 of above table) along the main streams. 
From their position these terraces appear to be somewhat older than 
the second bottom terraces. Along the minor streams, the sand ter- 
races appear to be the main terraces. Sand similar to that of which 
these terraces are composed covers some of the inter-stream areas and 
divides, up to altitudes of 100 feet. This is the Ozark or Conecuh 
sand. ‘This inter-stream sand is compared to the inter-stream phase 
of the Columbia, as developed at other points on the coastal plain, 
especially farther north. While therefore the first three of the Pleisto- 
cene formations, as shown in the table, are essentially equivalent, the 
fourth seems to be somewhat older. 
Along the principal streams there are “third terraces’’ which are 
50 to 100 feet above the second bottoms. These third terraces con- 
sist of red loam with more or less gravel beneath it. ‘Their constitu- 
tion is in all respects comparable to the constitution of the Lafayette 
formation, as developed at higher levels. These third terraces sustain 
the same relation to the Lafayette formation which covers the inter- 
stream areas, that the sand terraces (No. 4) do to the Ozark or Con- 
ecuh sand, though the third terraces and the Lafayette lie at higher levels 
than the sand terraces and the Ozark and Conecuh sands. ‘The third 
terraces are very much wider than the second bottom terraces, and 
are, as all their relations show, considerably older. 
The Lafayette formation finds its normal development above the 
third terraces. Dr. Smith’s suggestions concerning the origin of this 
formation are of interest, and his classification of the same should be 
especially noted, in view of the fact that he has recently been quoted* 
as holding that the Lafayette is Pleistocene. His words areas follows: 
“The general appearance of the formation, and the demonstrably great 
amount of erosion which it had suffered before the deposition of the undoubted 
Pleistocene beds, would lead us to conclude that a long period of time and 
important physical changes occurred between the accumulation of the Lafay- 
ette and the Pleistocene deposits. For these reasons, the weight of evidence 
*UpHAM. Am. Nat. Vol. XXVIII., p. 979, 1894. 
