214 Observations upon the Geology and Paleontology 



unascertained depth below, as the boring did not reach 

 through it. It is thus known in this locality to be more 

 than one hundred and thirty feet thick. 



No. 2 is a compact, bluish gray limestone, changing to 

 a bluish brown. It is generally about six inches in thick- 

 ness, but sometimes thins nearly out. It is not inclined 

 to disintegrate or become fragmentary like bed No. 4, but 

 breaks more easily in the plane of stratification than by 

 cross-fracture. This is owing to the horizontal position 

 of the shells, with which it is crowded to repletion. In 

 consequence of the compactness of the stone, these shells, 

 as weU as all other fossils it contains, are badly preserved. 

 The mineral composition, texture, and color, together with 

 its abundance of fossils, are remarkably uniform. 



No. 3 is a very thin band of oolitic limestone, seldom 

 exceeding three inches in thickness. The egg-like concre- 

 tions composing it are very distinct. Fossils are frequently 

 found in it, but are not so abundant as in No. 2. Although 

 so thin, it retains its place persistently throughout almost 

 the entire exposure under consideration. 



No. 4 is composed of a very compact, dark gray lime- 

 stone, having a conchoidal fracture. It is thickly mottled 

 w^ith brown, sandy patches, harder than, but similar to, the 

 stone of the overlying bed. The whole is very fragmen- 

 tary, and, when exposed to the weather, falls into fragments 

 similar in size to the stone used for macadamizing the 

 streets. This bed has been pronounced unfossiliferous. 

 In some places it is so, yet fossils are frequently found in 

 it, but not abundantly. They are sometimes found con- 

 gregated in small colonies, only a few feet in extent. Its 

 lines of stratification are rather distinct, but the bedding 

 is broken up by the fragmentary character of the mass. 

 Zinc blende, in small lamellar and crystalline masses, is 

 frequently found in it, as well as numerous cavities filled 

 with calcareous spar. 



