1855.] 



257 



Observations on the Eocene deposit of Jackson, Mississippi, with descriptions oj 

 thirty-four new species of shells and corals. 



By T. A. Conrad. 



The following table will show the order of succession of Eocene groups ; but 

 is not pretended to be more than an exposition of my limited knowledge of them, 

 though they are doubtless presented in the true order of superposition. Further 

 research may develope intercalated groups. No. 6, is probably synchronous with 

 the Orbitulite limestone of St. Stephens, Alabama, as its two most prominent 

 fossils are very abundant in this stratum at Vicksburg. No. 5, is the lowest bed 

 exposed in the bank of the Mississippi river, at Vicksburg. Col. Wailes found 

 a large Ostrea on the top of the Jackson group, which is probably the shell 

 referred to in No. 5. It would be convenient to designate these sub-divisions 

 thus: Claiborne group; Jackson group; Vicksburg group; St. Stephens group ; 



8. 



7. 



GROUPS OF CHARACTERISTIC FOSSILS. 



Crassatella Mississippiensis, Area Mississip- A 

 piensis, Meretrix sobrina, M. imitabilis, 

 Turbinella Wilsoni. 



Corbula alta, Natica. 



6. Pecten Poulsoni, Orbitulites Mantelli. 



5. 



4. 



3. 



2. 



1. 



Ostrea Georgiana? 



Umbrella planulata,Cardium Nicolleti, Co- 

 nus tortilis, Cyprasa fenestralis, Galeodia 

 Petersoni, Rostellaria extenta, &c. 



Crassatella alta, Pectunculus stamineus, Me- 

 retrix aequorea, Gratelupia Hydii, Leda 

 ccelata, Crepidula lirata, &c. 



Ostrea sellaeformis. 



Newer 



Eocene, 



Vicksburg. 



Cardita densata. Cyclas 



Older 

 Eocene, 

 Jackson. 



Older 



Eocene, 



Claiborne. 



Alabama river, 



Nos. 1 to 3 represent the Claiborne group; 4, Jackson group; 6, the St. 

 Stephens group ; 7 and 8, the Vicksburg group. When a group of corresponding 

 fossils is to be found elsewhere, its relative position can be stated by referring to 

 the typical subdivision which contains many identical species. 



Since my discovery of the Eocene formation of Claiborne, Alabama, in 1832, 

 by means of fossil shells collected by Judge Tait, numerous localities have been 

 found in the southern States, and characteristic fossils have also been obtained 

 by Major Emory, in Western Texas, and even in California, by Mr. Blake. 

 Localities widely separated contain some species in common, but I did not anti- 

 cipate that groups would vary to the extent they do in the three localities of 

 Claiborne, Alabama, Jackson and Vicksburg, Mississippi. Col. B. L. C. Wailes, 

 of Mississippi, has lately discovered a new group of Eocene fossils at Jackson, 

 in which none of the Vicksburg species occur ; and of forty species, five only 

 are identical with Claiborne fossils. One of the Jackson shells, Cardium Nicolletti, 

 Conrad, was first discovered in the bank of Red river, Washita ; and, therefore^ 

 this latter locality will probably prove to belong to the same division of the 

 Eocene as that of Jackson. The Mississippi deposit described by Col. Wailes, 

 is a group of shells chiefly, of more than ordinary beauty and preservation, 

 imbedded in sand of a gray color, consisting of fine angular grains of quartz and 

 minute fragments of shells. One of the species, Cyprcea fenestralis, is closely 



