Bulletin 12 136 



grained, arenaceous black shale, homogeneous throughout, and 

 having a thickness of from 100 to 120 feet in southern Indiana. 

 South of Louisville the New Albany shale becomes greatly re- 

 duced in thickness. At Brooks Station it is less than thirty feet 

 thick 



South of the Ohio the New Albany shale has been found rest- 

 ing unconformably on the beds below. Near Brooks Station the 

 shale was found resting unconformably on irregularly eroded 

 Devonian limestone. 



Devonian Limestones. 



All of the Devonian beds at the Falls of the Ohio below the 

 Black shale were at one time referred to the Upper Helderberg 

 formation by Prof. Hall. He afterwards recognized the two-fold 

 chara(fter of the faunas which they contain and correlated them 

 with the Corniferous and Hamilton formations of New York. 

 The Devonian near the Ohio in Indiana and Kentucky is readily 

 separated into two divisions, which are easily distinguished from 

 each other both by lithological and paleontological charadlers. In 

 order to avoid further possible confusion in referring to the 

 fossils of these divisions it will perhaps be best to use local names 

 instead of the names of the New York formations hitherto used. 

 For the upper portions of these beds, which are very arenaceous 

 and silicious, the name "Sellersburg beds" is proposed, to include 

 the beds from the New Albany shale down to the lowest beds 

 worked at the cement quarries. They are extensively worked 

 near Sellersburg for cement. These beds consist of a fine-grained 

 calcareous sandstone from six to twenty feet thick and a thin bed 

 of limestone, which when present lies immediately under the 

 New Albany Black shale. 



The limestone lying between the Sellersburg beds and the 

 Catenipora beds of the Niagara are well exposed at the Falls of 

 the Ohio between Jefferson ville and the -mouth of Silver creek, 

 and may be called the Jeffersonville limestone. 



The Devonian formations below the New Albany shale are fre- 

 quently entirely absent in the Kentucky se<5lions, and where 

 present they are usually represented by only a few feet of strata. 

 The Sellersburg beds have not been seen south of Louisville. 

 The attenuated character of the lower Devonian beds in Ken- 



