1846.] LYELL ON THE NEWER DEPOSITS OF NORTH AMERICA. 409 



Lea were derived. The annexed section will explain my view of 

 the structure of this country better than a detailed description. 



Section showing the position of the Nummulitic Limestone near Claiborne. 



a. White eocene limestone, marl, &c. 



b. Nummulitic limestone (eocene). 



c. Blood-red clay, yellow sand, &c. (eocene ?) 



I am informed by Captain Bingham the engineer, that some of 

 the hills between Clarksville and Creagh's, on the tops of which I 

 observed the nummulite limestone, are about 400 feet higher than 

 the top of the bluff at Claiborne. 



Seventhly, the conclusion last-stated will make it necessary in 

 future to omit from all lists of American cretaceous fossils such 

 species of shells as have been considered secondary, simply on the 

 ground of their occurrence in the nummulite limestone of Ala- 

 bama. The fossils which I have met with most abundantly in the 

 latter are the Nummulites Mantelli and Pecten Poulsoni. I have 

 however many others, especially casts of shells and corals, which 1 

 shall hereafter describe. The nummulitic formation is from 50 to 

 100 feet in thickness, consisting for the most part of a soft cream- 

 coloured stone, hardening on exposure, while in other beds it is 

 highly indurated. In its lower portion, where it joins the ordinary 

 white limestone, I found Pecten perplanus, Ostrea panda and Pla- 

 giostoma dumosum. Lunulites and other corals also occur in this 

 rock. The recognition of the true place of this limestone in the 

 series will remove almost every fossil from the list of those species 

 which were still supposed to be common to the cretaceous and ter- 

 tiary groups of the United States. 



Eighthly, I have visited several of the principal localities where 

 the bones of that gigantic cetacean, called Basilosaurus by Dr, Har- 

 lan and Zeuglodon by Mr. Owen, have been discovered in Clarke 

 county before-mentioned. These bones are everywhere in the same 

 geological position, namely in the eocene white limestone, below 

 tha level of the nununulitic rock and above the beds which contain 

 the greater number of perfectly preserved eocene shells, such as 

 Cardita planicosta and others. 



Ninthly, on Creagh's plantation and about four miles and a half 

 S.W. from Clarksville, 1 visited the spot where Mr. Koch i)r()cured 

 in 1845 the head and part of the vertebral column, about tliirty feet 

 in length, of the Zeuglodon, called by him Ilydrarchos. I was ac- 

 companied by Mr. William Pickett, a gentleman who also assisted 



