126 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 52 



Mr. Foerste applied the name Louisville limestone to this particular 

 division of the Silurian. The fauna is a large one and is well 

 known through the works of Hall, Lyon, Nettelroth, and others. 



The succeeding beds of Major Lyon's classification have offered 

 more difficulty in exact correlation. The scarce and undiagnostic 

 fossil evidence afiforded by the Devonian black shale has made it 

 difficult of exact correlation. Following the determination by Hall, 

 and the recent, more detailed studies of Kindle, it is now generally 

 correlated with the Genesee and Portage shales of the New York 

 section. The Devonian limestones, on the other hand, furnish an 

 abundance of fossils ; but here the difficulty first arose from a lack 

 of care in the exact location of the fossils in the section. It is only 

 in recent years that the horizons of the various species have been 

 accurately determined, and even now the geologic position of some 

 of the rare forms is in question. 



In the vicinity of Louisville the Devonian limestones are now 

 divided into three beds : ( i ) gray to blue crystalline limestone about 

 20 feet thick, overlying the Niagaran strata and comprising the four 

 beds in Major Lyon's section between his Catenipora bed and the 

 hydraulic limestone; (2) a fine-grained silicious limestone or cement 

 rock (the hydraulic limestone of Lyon), and (3) a thin bed of purer 

 encrinal limestone which is overlaid by the Devonian black shale. 

 These limestones were originally considered together as of Upper 

 Helderberg age by Hall, but later the lowest division was correlated 

 with the Corniferous (Onondaga) of New York, and the upper two 

 members were referred to the Hamilton. 



In 1899 Kindle applied the local name of Jeffersonville limestone 

 to the lowest division and proposed Sellersburg beds for the cement 

 rock and overlying purer strata. The following year Siebenthal 

 introduced tlie new name Silver Creek hydraulic limestone for the 

 cement rock and restricted the name Sellersburg to the overlying 

 beds. 



Mr. Nettelroth and other local collectors used no special geo- 

 graphical names in locating the horizons of their fossils, but the 

 vari(ius beds in the section were very well known. Mr. A'ictor Lyon 

 has kindly ftu-nished me with a list of the local names api^lied to 

 these beds at that time, and these, in the form of a section with the 

 more recent correlations, are given below. 



