110 The Lower Devonian Deposits oe Maryland 



argillaceous limestones, as in Maryland. The general sequence of faunal 

 zones is also similar, the Chonetes jersei/ensis fauna being present in the 

 lower strata, and Tentaculites gymcanthus in the upper beds. 



The upper limit of the Keyser is probably limited by an unconformity 

 which separates it from the overlying Coeymans or New Scotland. The 

 basal part of the Oriskany is a cherty shale suggesting the Shriver Chert 

 member at the base of the Oriskany of Maryland. 



The Helderberg and Bossardville limestones are well exposed in eastern 

 Pennsylvania where they agree in fauna and lithology with the correspond- 

 ing beds of New Jersey with which they are continuous. The discussion 

 of the latter area will therefore apply to them. 



Correlation vs^ith New Jersey. — The Lower Devonian and Upper 

 Silurian limestones of New Jersey were divided by Weller' into the fol- 

 lowing formations : 



r] 



-Becraft 

 Devonian -j New Scotland 



l-Coeymans 

 fManlius 

 J Rondout 

 1 Decker Perry 

 I Bossardville 



Silurian 



The Bossardville of New Jersey so closely resembles the formation of the 

 lame in central Pennsylvania that there is little doubt of their 

 il identity. The latter can possibly be traced southward into Mary- 

 land where it is tenned the Tonoloway. 



Weller subdivided the Decker Ferry into three faunal zones each char- 

 acterized by a definite association of species which he named as follows 

 in descending order : 



Rhynchonella lamellata zone. 

 Ptilodictya frondosa zone 

 Chonetes jerseyensis zone. 



The most diagnostic species of the lower zone is Chonetes jerseyensis 



associated with SchucJiertella decherensis, StenocMsma deckerensis, and 



Camarotcechia litchfieldensis. All of these and many others common in 



that zone are abundant also in the Chonetes jerseyensis zone of the Keyser 



of Maryland. 



• Pal. N. J., vol. iii, 1903. 



