Maryland Geological Survey 173 



Helderberg Formatio.v 



Vertical Total 

 New Scotland Member thickness vertical 



feet thickness 



Concealed. The concealed interval consists of fissile gray 

 shale. 



Gray crystalline limestone with interbedded white chert. The 

 latter forms almost the entire thickness of the unit and is in 

 courses 6 to 9 inches thick. Rhipidomella ohlata and Spirifer 

 perlamellosus, 4.4, Schizophoria multistriata 13.0 34.0 



Gray crystalline limestone with several chert layers 2.0 21.0 



Medium-bedded gray limestone with but few chert layers. 

 Dalmanites pleuroptyx, Leptwna rhomboidalis. Dalmanella 

 perelegans, Meristella arcuata occur abundantly throughout, 

 and less abundant but common are Spirifer cyclopterus, S. perla- 

 mellosus. Rhipidomella oMata, Schuchertella woolworthana, 

 Fenestella idalia, 2.4, 2.9; Orthopora rhombifera, 2.9; Ortho- 

 pora regularis, 2.9; Monotrypa tabulata, 2.9; Stropheodonta 

 arata occurs at 8.4, 4.9, 3.8; Spirifer macropleurus, 7.9, 6.7, 6, 3.7 

 (?); Stropheodonta planuln fa. 6.7, 3.8; Orbiculoidca sp., G; Eato- 

 nia medians, 4.9, 4.3; Lichenalia sp., 4.3, 3.8, 2.9, 2.4, 2; Stro- 

 phonella leavenworthana, 4.3, 3.8, 2.9, 2.4, 2, 0.4 feet; Stropho- 

 nella punctulifera. 3.8, 2.9; Uncinulus sp., 2.9; Cyatho- 

 phyTloid coral and Uncinulus nucleolatus, 2.9; Leptanisca con- 

 cava, 2.4; Actinopteria cummunis and Tentaculites elongatus, 

 2.8; Chonostrophia helderbergiw, 2; Atrypa reticularis and Dal- 

 manella eminens at 0.4; crinoids, 3.8. Near base occur Ano- 

 plotheca concava (aa), Spirifer cyclopterus, Schuchertella wool- 

 worthana with fine striae, Cypricardinia cf. sublamellosa. Tenta- 

 culites sp., Leptwna rhomboidalis 9.6 19.0 



Yellow shale. Spirifer perlamellosus 0.8 9.4 



Thickness of New Scotland member exposed 25.4 



Coeymans Member 



Medium-bedded gray limestone with a chert layer at top of 

 unit. Gypidula coeymanensis (aa), Dalmanella perelegans, 

 Spirifer cyclopterus. Leptwna rhomboidalis, Strophonella lea- 

 venworthana occur throughout. At the top are found Stro- 

 phonella punctulifera, Meristella sp., Schuchertella woolwor- 

 thatia with fine strise; and Atrypa reticularis 



Single bed of massive gray limestone weathering to a ridge 

 which stands out as the " Backbone." Chert layers 6 inches 

 thick at top and near middle. Limestone pebbles at base. 

 Gypidula coeymanensis. Leptana rhomboidalis. Atrypa reticu- 

 laris occur abundantly throughout; Strophonella punctulifera, 

 5.9, 2.9; Dalmanites pleuroptyx, Strophonella leavenworthana. 



