EASTERN AND SOUTHERN UNITED STATES. 
151 
occur, that in Mississippi are found in the Vicksburg beds alone, viz. : Madrepora Missis- 
sippienm, Orbitoides Mantelli, Avicula argentea;Terehra tantida, T. divimra, Pleurotoma 
porctllana, Pyrula (2 species, undetermined), Phorus Immilis, and Rmgicula Alissis- 
sippiensis. To this is also added Ostrea Georgkma. The occurrence here claimed, 
of Orbitoides Mantelli and Ostrea Georgiana, two forms whose horizons in Mississippi 
appear to be so trenchantly severed from the Jackson, would seem to throw some 
doubt upon the accuracy of the boundaries of the various formations as laid down. 
South of the Vicksburg line the deposits of the Grand Gulf group, destitute of 
fossil remains just as in Mississippi, extend across the State ; they are succeeded to 
the south by the deposits of what Hilgard has termed the “ Port Hudson Group ” 
(Post-Pliocene ; “ Coast Pliocene ” of Mississippi). 
ArJcansas. 
About one-half of this State is occupied by the Tertiary formation, concerning 
whose development we are unfortunately provided with but very few reliable data. 
The various divisions have not yet been paleontologically defined, but probably the 
series includes the pre-Claibornian, the Claiborne, and the Jackson. The presence of 
the last is inferred from its position in the State of Louisiana, where, as it has been 
seen, it extends to the Arkansas boundary. Lignitic deposits occur largely throughout 
the Tertiary area, and while some of these doubtless represent the basal beds of the 
Eocene, as has been premised by Owen,* * * § , others (of the S. E. section of the State) not 
improbably form the continuation of the Jackson lignites of Louisiana. Claiborne 
{ossAs—Cardita planicosta, Cytherea (probably C. NuttaiK), Corbula oniscm, PsetidoUva 
vetusia, Turritella (probably T. carinata), and Voluta (F. Sayana?)—ha.ve been 
obtained, among other localities, at “ White Bluffs ” on the Arkansas Biver (about 
latitude 34° 27'), and much the same assortment from the neighborhood of Madison, 
St. Francis Co., on Crow creek.f 
Texas. 
The Tertiary formations of this State are as yet too imperfectly known to admit 
either of an absolute localization of the various boundary lines, or of an accurate 
subdivision into the minor geological groups. It may be safely assumed, however, 
from the geological conformation of the neighboring States, that all, or nearly all of the 
divisions ranging from the Eo-Lignitic to the Grand Gulf inclusive, are represented, 
and that the position occupied by these follow each other in regular succession, 
beginning with the oldest, from the interior coastward, with a general dip to the 
southeast or east. The geological notes on this region by Schott, Hall, and Conrad,^ 
and of Shumard§ and Buckley H are exceedingly meagre and unsatisfactory, and give 
us barely more than a general idea as to Avhere the Tertiary formation exists. 
* “Second Kept. Geol. ReconTofthe Middle and Southern Counties of Arkansas,” 1860. 
t Owen, op. cit., pp. 35, 152, and 417 ; Plate IX. 
\ Emory’s Report, Mexican Boundary Survey, i, 1857. 
§ First Report of Progress, Geol. and Agr. Survey of Texas, 1859. 
II First Annual Report, 1874 ; Second Annual Report, 1876. 
