EASTERN AND SOUTHERN UNITED STATES. 
147 
embayment, and meet tbeir continuation on the other side of the river in the State of 
Mississippi. 
Siliceous and Calcareous Claiborne. — There can he no question that the deposits 
we have recognized in Alabama and elsewhere as the “ Buhrstone ” and the “ Clai- 
bornian ” have their exact counterparts in Mississippi, and that these correspond in a 
general way with what Hilgard has designated the “ Siliceous Claiborne ” and the 
“ Calcareous Claiborne ” respectively. The former extends in a belt, some twenty 
miles wide, westward from the Alabama line nearly half across the State, reappearing 
as outliers in Carroll and Attala counties in the deposits of (near) Valden and Shongalo, 
to which reference has already been made in the discussion of the Northern Lignite. 
Among its commoner fossils are Cardita plan'costa, G. rotunda, Gardium Nicolleti, 
Ostrea divaricata, Pecten Lyelli, and Voluta petrosa. From the locality of Enterprise, 
on the Chickasawhay River, Clarke County, situated on the line of contact of the 
“ Siliceous ” and “ Calcareous Claibornes,” as indicated by Hilgard, Mr. Conrad in 
1865 described the following species of mollusca, claimed to be all new, “ and 
distinct from those of any other locality from which fossils have been sent to the 
Academy ; ” * Ostrea faldformis, Ehurneopecten scmtillatns, Arcoperna filosa, Nacula 
spJieniopsis, Leda linifera, Axincea {Pectuncrdus) inequistria, A. dupUstria, Gonldia 
pygmoea, Grassatella producta, Protocardia lima, Gyclas curta, Sphcerella hidla, Alvei- 
nus minuta, Gytherea securiformis, G. annexa, Tellina eburneopsis, T albaria, TelUnella 
linifera, Gorhula filosa, Doliopsis quinquecosta, Turritella perdita, and Mesalia? 
arenicola.^ 
The true “ Claibornian,” consisting of blue marl and white marlstone, is but very 
feebly developed in the State, occupying a narrow strip, some thirty to forty miles in 
length, mainly in Clarke County, wedged in between the Buhrstone and Jackson. The 
fossils, in distinction to those of the corresponding Alabama deposit, are very imper- 
fectly preserved, and in most cases specifically unrecognizable. The leading forms 
are: Ostrea sellceformis, 0. divaricata, Pecten Lyelli, Gorhula gihhosa, (C. onisus, 
Conr. ; G. rugosa, Lam.) and Voluta petrosa. 
Jackson and Vicksburg. — The deposits of the Jackson and Vicksburg (Oligo- 
cene) periods occupy parallel bands passing across the State, disappearing in the west 
under the Mississippi alluvium. The most distinctive fossil of the former is the 
Zexiglodon, and of the latter Orhitoides, represented by two (0. MantelU, 0. nupera), 
or more species. Although by several observers, including Conrad, the fossils here 
indicated have been at various times referred to as occurring together in the same 
deposit, there can be but little question, as has been insisted upon by Hilgard, that 
* Am. Joum. of Conchology, i, pp. 137-41. 
f Most of these are doubtless distinct, but it would be difidcidt, if not impossible, to distinguish between 
Ostrea falcifornm and 0. dkaricata, Nucula sphceniopsis and N. omla, and Cytherea annexa and C. pcrovata, 
common Claiborne fossils. 
