188 On the Nummulite Limestone of Alabama. 



As the subject stands at present, then, we have no right to in- 

 fer from the presence of an Orbitolite however abundant, that 



period 



and our own times.* 



>poch 



obscurity 



paper 



Alabama had been involved, it having been considered sometimes 

 as an upper cretaceous group, and at others as intermediate be- 

 tween the cretaceous and the eocene formations. The accompa- 

 nying section from Claiborne bluff to Bettis's Hill, near Macon in 

 Alabama, may serve to explain the relations which I found to 

 exist between the white limestone group of the south, compris- 

 ing the successive formations 1, 2, 3, and the overlying group 4, 

 which is perhaps of equal thickness but which from the absence 

 of calcareous matter rarely yields organic remains, and those con- 

 sisting only of silicified casts of shells and corals. This upper 

 formation (4) is composed of variously colored red, pink and 

 white sands, and of yellow ochre-colored sands, white quartzose 

 gravel and sand with beds of chert and flint, blood-red and 

 pink clays and clays of white kaolin or porcelain earth all hori- 

 zontally stratified. I could find no fossils in those in Alabama, 

 and only conjectured that they are of eocene date from the anal- 

 ogy of Georgia, where a deposit of the like aspect and nature and 

 occupying a similar position contains eocene shells and corals. I 

 formerly explained in 1841-42, the relative position of the upF r 

 clay and sands with flint of the burrstone formation of Georgia 

 to the underlying white limestone and marl of the state of South 

 Carolina, in a diagram published in the Journal of the Geol. Soc., 

 vol. i, p. 438, where the newer group is represented as resting on 

 the eocene limestone of Jacksonborough, near the Savannah river. 

 It appeared in that case as in Alabama, that the older calcareous 

 strata of limestone and marl, had undergone great denudation and 

 had acquired a very uneven surface, having been shaped into hills 

 and valleys, before the incumbent clays and sands were thrown 

 down. 



At the bluff on the Alabama River at Claiborne, where so rich 

 a harvest of fossils has been obtained, especially in some of the 

 beds of No. 2, we see at one spot called " The old landing," f hat 

 nearly the whole precipice in its lower one hundred and sixty 

 feet, exposes to view the calcareous beds 1 and 2, covered *»» 

 about twenty feet of red clay and sand. Whereas at the distance 

 of less than a mile from this spot, the upper formation No. 4, oc- 

 cupies more than one hundred feet of the face of the same clifl 

 from its summit, while at the base the lower members of the cat- 



"The PJagiostoma dumosum of Morton, is decidedly a Spondylus-" 



