22 INTRODUCTION. 



lion which is so remarkable, and passes through the whole 

 extent of South Alabama, called the Shell Limestone 

 Country, embraces this bluff. The southern edge of this 

 Formation commences about ten miles south of this place. 

 It is, no doubt, about one hundred miles wide from south 

 to north, in this part of the state. It is believed that this 

 limestone tract takes its beginning at the gulf, in the 

 neighbourhood of St Mark s and Tallahassee, and extends 

 from that point north west, through the whole of this and 

 the state of Mississippi, and is said to terminate at the 

 Chickasaw Bluffs, in West Tennessee. This Formation 

 is probably of the same nature with that which extends 

 through South Carolina, Georgia and Florida, parallel to 

 the sea coasts, and terminates on the gulf of Mexico, at 

 or about St Mark s. The course of this Atlantic Forma 

 tion is from the north east to the south west. The coun 

 try between the Shell Limestone tract in this state, and 

 Mississippi and the gulf, is a barren sand, with the long 

 leaf pine (Pinus australis), &c. as its principal forest 

 growth.&quot; 



With the specimens then sent, was received a short stra- 

 tagraphical account of each which is here inserted. 



&quot; No. 1 is a specimen of the stratum, from the water 

 line up about one hundred and twenty feet, extending be 

 low the water as far as can be discerned by the eye.&quot; 



This specimen was nearly six inches square. It is a soft 

 calcareous rock, containing eleven per cent of carbonate of 

 lime,* with occasional specks of mica, and small cells filled 

 with carbon. In breaking it up, to present as much surface 

 as possible, I examined it carefully, to endeavour to identify 

 the fossils contained in it, but these could only be seen in a 

 very imperfect state, and almost universally in fragments. 

 They consisted generally of Flustrcv, Cardm, Corbulce, Os- 



* To the kindness of Dr J. K. Mitchell I am indebted for the analysis 

 of these specimens. 



