102 The Lower Devonian Deposits of Maryland 



Corriganville Lower Stromatopora Reef. — Two massive Stromatopora 

 reefs occur in the upper part of the Keyser at the Devil's Backbone and at 

 many other localities both east and west of Cumberland. They seem to be 

 the most persistent reefs in the Keyser member and were long considered 

 the only ones. Both reefs abound in Stromatopora constellata and 

 Favosites helderhergios var. prcecedens. They are here termed the Cor- 

 riganville Lower and Upper coral reefs respectively, because of the fine 

 exposure at the Devil's Backbone at Corriganville. 



I'entaculitcs gyracanthus Suhzone. — A shaly limestone occurs between 

 the Stromatopora reefs that abounds in Tentaculites gyracanthus. At 

 Keyser and Dawson this subzone contains also a great profusion of 

 Schuchertella prolifica and Merisiella prcenuniia. 



Corriganville Upper Stromatopora Reef. — The last-named subzone is 

 overlain at the Devil's Backbone and various other places by a reef similar 

 to the one below it and containing the same species. 



Leperditia Suhzone. — The upper beds of the Keyser member are char- 

 acterized at the Devil's Backbone and at many other localities by a pro- 

 fusion of a late form of Leperdiiia alia named L. altoides. The beds of 

 this subzone are usually somewhat shaly and are interbedded with thicker, 

 dark brown strata. The following species also occur in it : Schuchertella 

 prolifica, Meristella pra'?iunUa, Tentaculites gyracanthus, Orthoceras 

 rigidum. 



Coeymans Member 



The Coeymans member is too thin (never more than 13 feet) to render 

 an analysis of its faunules valuable. 



New Scotland Member 



The New Scotland is divisible, lithologically, into two very distinct 

 parts, the lower being a very cherty limestone and the upper a fissile shale. 



The lowest beds of limestone contain less chert than the other strata. 

 Chonostrophia lielderhergice is abundant near the base of this member at 

 the Devil's Backbone and at Dawson, at which horizon Spirifer perlamello- 

 SII.S also usually makes its first abundant appearance. Meristella arcuata 

 becomes profuse in certain sections a short distance above the base. 



