GEOLOGICAL SOCIETY OF PENNSYLVANIA. 243 



others of different shades of grey, from light ash grey to 

 blackish grey, also of different textures ; some granular, 

 others- compact, but most of them exhibiting an oolitic 

 structure : the oolitic limestone is always light, sometimes 

 nearly white. Some of these strata are without any 

 organic fossils, while in others they are densely accumu- 

 lated. This series, which belongs to an old deposition, 

 as it is always below our coal strata, is not known, I be- 

 lieve, to exist in Europe. It is particularly character- 

 ized by several species of pentremites, stylines, calamo- 

 pora, and some other which no doubt will constitute some 

 new genera. 



_ This formation, which I have traced from near Hunts- 

 ville, Alabama, to near the Cumberland river, Tennes- 

 see, and which must be considered as the base of Cum- 

 berland mountain, is lost, at an elevation of about 1600 

 feet above the sea, under the coal strata which form the 

 summit level of Cumberland mountain. 



It is in the above described formations of oolitic lime- 

 stone, which I have nowhere found above the coal or 

 alternating with it, that Big Bone cave is situated. 



