Mississippi and Alabama. 205 



2. Bluish gray marl, like the above, containing very little 

 grit. Fossils — Pecten Poulsoni Mort., Ostrea VicJcs- 

 burgense Con., (Jardium diversion Con., Crassatella 

 Mississippiensis Con., Sigaretus Mississippiensis Con., 

 Orbitoides Mantelli Mort., Gytherea imitabilis Con., 

 Turritella Mississippiensis Con., Cytherea sobrina 

 Con., Mitra conquisita Con., Turbinella protracta 

 Con., Madrepora Mississipjriensis Con., Githara Mis- 

 sissippiensis Con., Area Mississippiensis Con., Terebra 

 divisura Con., Plenrotoma congesta Con., P. tenella 

 Con., P. (Scobinella) coelata Con., i 3 . cristata Con., i-*. 

 cochliaris Con., Aporrhais lyrata Con., Caricella 

 demissa Con., Oliva Mississippiensis Con., Triton 

 crassidens Con., T 7 . abbreviates Con., Solarium triline- 

 atam Con., Picks Mississippiensis Con., Capidus* 

 Americanus Con., Cyprea lintea Con., Phorus humilis 

 Con. ... 6 feet. 



The strata of this section overlie about twenty-five feet of 

 white limestone which rests immediately upon the top of sec- 

 tion 3. These marls are overlaid by white limestone, hard 

 ledges of which are seen cropping out of the river bank below 

 the ferry at this point. The marl gradually sinks out of view, 

 and is entirely submerged, within a short distance below the 

 ferry. 



There is at Yazoo City an exposure sixty feet thick of gray 

 calcareous clays which resemble very closely No. 1 of my 

 sedtion 1. These clays corrtain Ostrea pandceformisf Grabb, 

 Venericardia planicosta Blain., Pseudoliva perspecliva Con., Nu- 

 cula magnifica Con., Natica permunda Con., Cytherea sobrina 

 Con. and Zeuglodon cetoides vertebras. 



These observations, I think, establish beyond dispute the re- 

 lation of the Jackson beds to the Orbitoides limestone and marl 

 beds of Byram station. The river, at the time, was at a very 

 low stage, affording excellent sections. 



As has been observed by Smith £ the lower portion of Tuo- 

 mey's White Limestone in Alabama forms a stiff black prairie 

 soil, with a growth of hickory and oak. The upper portion, on 

 the other hand, is characterized by slightly undulating open 

 " piney woods" with numerous limesinks. The former, Jack- 

 son of Hilgard, is identified by Spondylus dumosus Mort., 



* Rather a strange association ; the species was described from Jackson and 

 has not before been found in Vicksburg strata. 



fDr. White (Fossil Ostreidse of North America), says of this Ostrea: "It is 

 described from tbe Cretaceous of Mississippi, but not having been figured it seems 

 impracticable to identify it." The fossil mentioned above answers very well to 

 G-abb's description and is found in close proximity to the original locality. From 

 the associated fossils the strata are plainly Tertiary, though the black soil is apt to 

 mislead one. 



% Geol. Sur. Ala., 1881-82, page 236. 



