190 On the Nunvmulite Limestone of Alabama. 



is cut off at the top of the bluff by the newer series of beds No. 4 



near 



Clarksville, the same No. 2 is found more largely developed. It 

 is characterized among other organic remains by a large Nautilus 

 allied to N. ziczac and by the gigantic zeuglodon of Owen. Near 

 the juncture of the mass with the incumbent Orbitolite limestone, 

 we find Spondylus dumosus, (Plagiostoma dumosum, Morton,) 

 Pecten Poulsoni, Pecten perplanus, Ostrea cretacea, in abundance. 

 No. 3 is a pure limestone, sometimes hard and full of Orbitolites 

 Mantelli. At Bettis's Hill the formation is about sixty feet thick, 

 and the upper beds are composed of a cream-colored soft stone, 

 which hardens on exposure to the air, is not divided by lines of 

 stratification, and is for the most part made up of Orbitolites of va- 



small 



! 



with specimens of Pecten Poulsoni. The origin of this limestone 

 like that of our white chalk, the softer varieties of which it much 

 resembles, is I believe due to the decomposition of corals, and 

 like our chalk downs, the surface of the country where it prevai 

 is sometimes marked by the absence of wood, by which all the 

 other deposits in this part of Alabama are continuously covered. 



but in some places, and at Bettis's Hill among others, the Orbitolite 

 rock produces what is termed a " cedar knoll ;" the red cedar. 

 Juniperus virginiana having exclusive possession of the ground. 

 I was much struck with the resemblance of such calcareous 

 tracks, covered with the trees above mentioned, to certain chalk 

 regions in the south of England, where the only wood which 

 grows on the white rock consists of yew trees accompanied her 



juniper 



At St. Stephens, on the left bank of the Tombeckbee ri ver, in 

 Alabama, a similar limestone with Orbitolites forms a perpendic- 



ular bluff. 



time 



~. u „. *. llKj nav^t ui me river at me time 01 my vi»« "- 



too high to enable me to collect fossils from the older beds at the 

 base of the cliff, but I was afterwards furnished with them 

 through the kindness of Prof. Brumby of Tuscaloosa. They 

 are imbedded in a ferruginous ochreous-colored sand, and consist 

 in part of shells common to Claiborne bluff, such as Terebra cos- 

 tata, Conrad, Cardita parva, Dentalium thalloides, Flabellum 

 cuneiforme, Lonsdale, Scutella Lyelli, Con., and several more. 



I shall now conclude by adverting briefly to the result of a 

 comparison which I made of the fossils contained in the eocene 



inland 



Mississippi 



position of which is indicated at 4a in the wood-cut 01 

 page, with those of other eocene beds forty-five miles furt 

 or eastward at Jackson, in the same state. In the former of the^ 

 at 4a, the Orbitolites Mantelli abounds, together with P<*J« 

 Poulsoni, Dentalium thalloides, Sigaretus arctatus, Con., Teiet* 



