Maryland Geological Survey 89 



suhglohosa, a species closely related to R. aquiradiata of New York. The 

 fauna of the Maryland Becraft is in many respects similar to that of the 

 New Scotland, but a closer approach to the Oriskany aspect is indicated 

 by the presence of Rhipidomella a^ssimilis, Phthorhyncha prcespeciosa, 

 Remselwria suhglohosa, Cyrtina rostrata, and Meristella lata. 



Becraft-New Scotland Boundary. — The upper limit of the Few 

 Scotland is shown by the transition from the New Scotland white chert 

 with a little intcrbedded limestone, to the Becraft limestone carr}'ing a 

 smaller amount of black chert. 



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COMPOSITE SECTION OF THE HELDERBERG FORMATION 



' Dark blue arenaceous limestone, with lumps of 

 black chert. The fauna is most abundant in 

 the upper half, where RensseUrria subglobosa 

 is the characteristic fossil. 



About 85 feet. 

 This member is absent west of Hancock. In 

 other eastern sections the thickness may at- 

 tain to 125 feet. 



Soft, bluish argillaceous shales, with some 

 harder layers and occasional manganese- 

 phosphatic nodules. 



Its faunule includes Dalmanella planiconvexa, 

 Rhipidomella oblata. Schuchertella wool- 

 worthana, Leptcena rhomboidalis, Anoplia 

 helderbergiw, Ambococlia umbonata ?, Spirifer 

 macropletirus. Meristella arcuata, and Trema- 

 tospira multistriata. 



Massive gray limestone, with bands of chert, 

 becoming thin bedded above, with partings of 

 shale; characterized by Spirifer macropleu- 

 rus. 



Massive, regularly bedded, blue-gray limestone. 

 The upper bed of this unit forms the promi- 

 nent ridge of the " Devil's Backbone," near 

 Cumberland. Containing Oypidula cwyman- 

 sensis. Spirifer cycloptcrus, and stems of 

 Lepocrinites. 



20 feet. 



