418 Miscellanies. 



and some Flustrce. It is only two feet in thickness. Above this rests 

 the depository of the fossils described in such abundance in the pres- 

 ent work. The bed is seventeen feet in thickness. It is composed 

 of a loose, quartzy sand of a brownish color. : the grains of which 

 are small and angular, and so slightly coherent as to permit the extri- 

 cation of the most delicate of its imbedded shells. The next stra- 

 tum distinguished, is only about eighteen inches in thickness, consist- 

 ng of a friable rock, easily separating into irregular pieces, and like the 

 subjacent one, composed of quartzy sand ; but whose grains instead 

 of being angular, are rounded, being held together through the inter- 

 vention of carbonate of lime. It contains casts of several shells, 

 among which were detected, Avicula, Venus, Crepidula and Tur- 

 ritella. Above this, reposes a thin layer, two feet in thickness, com- 

 posed of sand and shells slightly adhering by means of an argillo- 

 ferruginous cement which imparts a reddish brown stain to the aggre- 

 gate. The calcareous matter of the shells is so much decomposed 

 as to render it almost impossible to remove them from the surround- 

 ing matter. Aviculn, Venericardia, JVucuIa, Venvts., Teredo and 

 a {qv^ others were noticed among its imbedded fossils, as was also, 

 the ScuteUa crustuhides (Morton.) This layer and the preceding 

 are therefore with propriety believed to belong to the same epoch 

 with the stratum so rich in fossils, upon which they rest. Superior to 

 these comes, on, at the depth of forty five feet, the formation, com- 

 monly called in Alabama, " the rotten limestone^ 



It is an indurated marl containing scattered masses of dark green 

 sand, and contains Corbulce, JYuculce and some other bivalves which 

 could be identified with fossils in the three lower beds. " A small and 

 very thin Pecten with delicate ribs seemed the only shell which left 

 its trace in a calcareous state. On each side of the fracture a silvery 

 whiteness marks the deposit of this thin and fragile species. Su- 

 perior to the present stratum, which may be considered as the cap of 

 the Tertiary, is found the Diluvium of the country, forming a mantle 

 about twenty feet in thickness, composed of sand and gravel mingled 

 with clay. 



Mr. Lea, unhesitatingly refers the rich fossiliferous stratum and its 

 superior members to the same period as the London Clay of Fngland 

 and the Calcaire Grossier of Paris, remarking, that this deposit is 

 composed of siliceous sand, while that of the London Clay is argil- 

 laceous and the Calcaire Grossier is calcareous. It will therefore 

 fall within the Eocene period of Mr. Lyell. 



