186 The Lower Devonian Deposits of Maryland 



VI. Section at North Branch 

 The black chert bedp of the Shriver Chert member of the Oriskany with 

 a portion of the arenaceous Eidgely member above them are exposed at the 

 south end of Nicolas Mountain on the Oldtown Eoad about 1 mile east of 

 North Branch Station. The exposure is not complete enough to give 

 either the top of the Helderberg or the Oriskany-Eomney contact. This 

 and the Winchester Eoad exposures are among the best for fossils of the 

 Shriver Chert member. The rocks are in the center of an anticline which 

 is more plainly shown on the south side of the river. 



Oriskany Formation 



Vertical 



Shriver Chert Memher thickness 



feet 

 Light gray sandstone with much black chert in nodules and 

 thin layers. Spirifer murchisoni (aa), j?. arenosus (a), Meta- 

 plasia pyxidata (aa), Anoplotheca flabellites (aa), A. flmhriata 

 (t),A. dichtoma (c), Meristella lentiformis (r) ?, Schuchertella 

 hecraftensis (rr), Chonetes hudsonicus (rr), Orbiculoidea ampla 



(rr), Lingulapholis terminalis (c) 100.0 



Black or blue chert in nodular and lenticular masses with 

 considerable arenaceous material. Spirifer tribulis (a), S. are- 

 nosus (?), Meristella lentiformis (aa), Anoplotheca flabellites 



(aa), Anoplia nucleata (r), Eatonia medialis (r) 10.0 



Black or blue-black chert in nodular and lenticular masses 

 containing Spirifer tribulis (aa), S. paucicostatus (r), Meri- 

 stella lentiformis (rr) , Stropheodonta arctimuscula (r) 75.0 



Thickness of Shriver Chert member 185.0 



VII. Section near Collier's Run 

 On the east side of Nicolas Mountain, about 300 yards above the 

 Eomney-Oriskany contact near Colliers Eun on Williams Eoad, is an 

 excellent place for collecting Oriskany fossils. The following fossils were 

 obtained here: Spirifer arenosus (a), S. intermedins (r), 5'. cumber- 

 landice (a), S. tribulis (rr), Metaplasia pyxidata (a), Anoplotheca flabell- 

 ites (a), A. fimhriata (r), Eensselaivia marylandica (a), Beachia suessana 

 (c), Plethorhyncha speciosa (c), P. pleiopleura (r), Eatonia peculiaris 

 (aa), E. sinuata (rr), Stropheodonta magnifica (r), Rhipidomella tnuscu- 

 losa (a), Platyceras gelhardi (a), P. ventricosum (a), P. nodosum (c). 



