M\l(^l.\\lt (;i:()i.(»(!ic.\i, sruvicY (\:\ 



Creok, is coiiijjoscd ol' a thick JK-d of greensaiifl. ovcrhiiii by lliick-ljedded. 



indiiralcd layers of greensaml innrl. ii is ;icmridly soiiifuliat under .")<) 

 I'cct in tliickiioss. 



Tile I'aspolansa sul)sta;;e infliulcs Zones <S and "J. The l"oll<j\viiig 

 fossils arc restricted to this siibstage: 



Bythocypris >iiihtic(/ini/(i lliicli. JJiploiIoiit-i hkiiIIx, iocuhIx Clark and Miirlin. 



BythocypriH jjitrHix Uliicli. Critnndtellittx ulla (Conrad). 



Cytherelltt mnrlhoroviisix 11 rich. (<') Aslarte mitrylaiidica Clark. 



CythereUa mubmarginata Ulricli. C<iraUi(>pha(j<i brtj'uii Chirk. 



Cythereis bussieri Ulricb. Paten sp. 



Pleurotoma harrisi Clark. Platidia innryUmdicn Clark and Martin. 



Plenrofoma potomavennis Clark and Martin. Discoxpitrstt lutriunx Ulricli. 



Pleurotoma ducatcU Clark and Martin. Faxcipora snbramosa Ulrich. 



Pleurotoma childreni Lea. lieticuUpora dic/ioiiintii Gabb and Horn. 



Plewotoma piscatavensis Clark and Martin. Cavaria dumosa 11 rich. 



Pleurotoma tysoni Clark and Martin. Heteropora tecta Ulrich. 



Cancellaria graciloides Aldrich var. Membranipora rhniilniii I' I rich. 



Cancellaria sp. Membninipora spiculosa Ulrich. 



Cancellaria potomacenxix Clark and Martin. Membranipora angusta Ulricb. 



Mitra marylandica Clark. Bifluxtra torta Gabb and Horn. 



Mitra pomonkensis Clark and Martin. Eschara digitata Gabb and Horn. 



Latirus marylandicHs Clark and Martin. Litnulites reverxa Ulrich. 



Fusus subtenuis Heilprin. Cribrilina niodesta Ulrich. 



Trophon sublevis Harris. Cribrilina crassula Ulrich. 



Melongena potomacensis Clark and Martin. Lepralia subplana Ulrich. 



Tudicla marylandica Clark and Martin. ' Lepralia labioxa Ulrich. 



Metula marylandica Clark and Martin. Jfucronella aspera Gabb and Horn. 



Chryxodomus engonatus (Heilprin). Paracyathns marylandicnx Vaughan. 



Pseudoliva sp. BalanopJiylUa dexhiop/iyllnni Milne-Ed- 



Tritonium showalteri (Conrad). wards and Haime. 



Fusoficula juve7iis (Whitfield). Textxlaria gramen d'Orbigny. 



Morio brevidentata (Aldrich). Textnlaria sagittula Def ranee. 



Calyptraphorus jacksoni Clark. 2fodoxaria consoi'brina var. emaciata Reuss. 



Aporrhais potomacensis Clark and Martin. Xodosaria sandbergeri (Reuss). 



Litiopa marylandica Clark and Martin. Xodosaria obliqua (Linne). 



Scala potomacensis Clark and Martin. Jlargimda costata (Batsch). 



Scala sessilis Conrad. Cristellaria gibba (d'Orbigny). 



Scala carinata Lea. Cristellaria rotatnla (Lamarck). 



Turbonilla potomacensis Clark and Martin. Pohjmorphina lactea (Walter and Jacob). 



Odosiomia trapaquara (Harris). Piscorbina turbo (d'Orbigny). 



Niso umbilicata (Lea). Anomalina ammonoides (Reuss). 



Calliostoma sj). Anomalina grosser ugosa (Giimbel). 



Fissuridea marylandica Clark and Martin. 



The two zones recognized in the Potomac area are characterized as 

 follows: 



