370 W. B. ClarJc — Potomac River Section 



Aquia Creek Stage. — The most common species of the 

 Aquia Creek stage are Turritella mortoni confined chiefly to 

 zones 8 and 9, Gytherea ovata and Grassatella alwformis 

 confined largely to zones 2 to 7, Cucullwa gigantea mainly 

 found in zone 8, Ostrea compressirostra* most common in 

 zones 6 and 7, and Dosiniopsis lenticxdaris, for the most 

 part limited to zones 2 to 5. Other species found in this 

 stage are Thecachampsa marylandica, Trionyx virginiana, 

 Ischyrhiza (?) radiata, Myliobatis copeanus, Carcharodon 

 polygurus, Lamna (?) obliqua, Oxyrhina hastalis, Gdontaspis 

 elegans, Galeocerdo contortus, Nautilus sp., Tornatella bella, 

 Pleurotoma harrisi, Vohitilithes (Athleta) tuomeyi, Volutili- 

 thes sp., Caricella sp. Mitra marylandica, Pyropsis sp., 

 Fusus (Levifusus) trabeatus, Fusus (Strepsidura) perlatus, 

 Fastis sp., Fulgur argutus, Lunatia marylandica, Natica 

 cliftonensis, Turritella humerosa, Galyptrcea trochiformis, 

 Vermelus sp., Scala virginiana, Gibbula glandula, Solarium 

 sp., Gastrochcena sp., PholasiJ) petrosa, Coralliophagabryani, 

 Tellina williamsi, Panopcea elongata, Pholadomya mary- 

 landica, Lucina aquiana, Venericardia planicosta, Grassa- 

 tella aquiana, Leda protexta, Modiola potomacensis, Pecten 

 johnsoni, Pecten sp., Gstrea sp., Serpula sp., Paracyathus (?) 

 clarheanus, Turbinolia acuticostata, Fupsam?nia elaborata, 

 besides many species of Foraminifera. 



"Woodstock stage. — The Woodstock stage is characterized by 

 the following common species, viz : Protocardia virginiana, 

 Gytherea subimpressa, Gorbula nasuta, Gorbula oniscus, Gstrea 

 sellceformis, Pectunculus idoneus, Leda improcera, Leda 

 parva, Nucula magnifica, Lucina dartoni, Lucina uhleri, 

 Lucina ivhitei, Venericardia planicosta, Pingicula dalli and 

 Gylichna venusta. Among other species found at this horizon 

 may be mentioned Carcharodon polygurus, Lamna (?) obliqua, 

 Gxyrhina hastalis, Gdontaspis elegans, Galeocerdo contortus, 

 Cythere sp. Mangilia (Pleurotomella) bellistriata, Fusus 

 {Levifusus) trabeatus, Lunatia marylandica, Gadulus bellulus, 

 Teredo virginiana, Solemya petricoloides, Gorbula aldrichi, 

 Tellina virginiana, Gytherea ovata, Diplodonta hopkinsiensis, 

 Yoldia cultelliformis, Modiola potomacensis, Pecten rogersi, 

 together with numerous species of Foraminifera. 



Correlation of the Deposits. — By common consent the 

 diversified and extensive Eocene deposits of the Gulf area 

 have come to be regarded as the type for the eastern border 

 region and the various Eocene deposits of the Atlantic coast 

 states have been assigned to a position in this series, although 

 very different limits have been given by the different authori- 

 ties. The Eocene deposits of the middle Atlantic slope have 



* Several immature oysters found at this horizon bear a strong resemblance to 

 the young of Ostrea sellceformis. 



