106 The Lower Devonian Deposits of Maryland 



Total 

 vertical 

 thickness 



Vertica 



thicknts 



feet 



Concealed 6 185 



Limestone 1 179 



Shale 1 178 



Concealed Leptwna bed 8 177 



Rough shale 3 169 



Concealed 4 166 



Thin, smooth shale 0.5 162 



Concealed 8 161.5 



Coral bed 6 153.5 



Rubbly limestone 15 147.5 



Smooth limestone and shale 2 132.5 



Concealed 3 130.5 



Soft shale — Syringopora ? and Spha-rocystites 1 127.5 



Rhynchonella bed filled with Rhynclwnella formosa 5 126.5 



Crinoidal 0.5 121.5 



Firm blue limestone, Rhynchonella formosa 3 121 



Thin-bedded, wavy, Murchisonia minuta abundant 3 118 



Shaly limestone forming nodules. Beyrichia and Rhyn- 

 chonella globosa, Murchisonia at top 12 115 



Coarse limestone, Beyrichia abundant 4 103 



Thin-bedded yellow limestone 3 99 



Thin-bedded blue limestone 5 96 



Thin-bedded limestone. Leperdiiia abundant 1 91 



Concealed 40 90 



Thin-bedded limestone, dark, Leperditia 50 50 



Waterlime Beds. Thinner at top. 



An examination of the section by tlie writer showed that the Clarks 

 Mill beds embrace the Keyser and Tonoloway fonnations. The Tonoloway 

 comprises the lower 103 feet and is overlain by the Keyser. It is probable 

 that the Keyser is present in its entirety, the top of the Clarks Mill shale 

 being approximately the Coeymans-Keyser boundary. 



The upper strata of the Keyser are thin-bedded to massive but not 

 nodular limestone, while the lowest beds are nodular and somewhat shaly, 

 precisely as found in Mainland. The faunal succession is also quite 

 similar to that observed in the latter State, a rapid examination showing 

 the presence of the following zones of the Maryland section, enumerated 

 in descending order: 



