M\|{V[,\\D GEOLOGICAL SURVEY 89 



Of tlie list above given, Levifusus Irabeaius, Pyrula penila vur., Ostrea 

 sellaefurtuLs and Trujonoarca decisa are confined to the Nanjemoy stage. 



The folh^wing Nanjenioy species have been found in the U|)per Clai- 

 bornian: 



Pyrula penitd var. ConnxA. Corbtda oniiicuH Conrad. 



Lunatia rnaryhmdica Conrad. Oxtren HcUaeforiniH Conrad. 



Calyptraea aperta (Solander). Pleria liiaula (Conrad). 



None of these species are confined to the Upper Claibornian and two 

 of* them only, Pyrula penita var. and Ostrea sellaeformis, are dis- 

 tinctively Nanjemoy forms. 



The following species occur in the Jacksonian, viz.: 



Cadulits ubniptiix Meyer and Aldricli. Pecteu dalli Clark. 



Corbula onhciis Conrad. Ostrea (Gyphaeostrea) vomer (Morton). 



None of them, however, has any special significance. 



It is thns shown that the Nanjemoy has faunal relationships both 

 with the Chickasawan (and especially with the Upper Chickasawan) 

 and with the Lower Claibornian. But in the Nanjemoy the lack of par- 

 allelism in the succession of faunas between the Middle Atlantic and 

 Gulf regions is even more noticeable than in the lower beds. The only 

 conclusion which can be drawn is that the Xanjemoy of Maryland rep- 

 resents such portion of the Chickasawan as lies above that represented 

 by the Aquia, while the occurrence of the highly characteristic species, 

 Ostrea sellaeformis, in the Nanjemoy stage in Maryland, although not 

 so numerously or typically represented as in the still higher strata in 

 central and southern Virginia, points to the possible Lower Claibornian 

 age of the highest beds of the Maryland Eocene. 



Geological Criteria. 

 The lithological and stratigraphical characteristics of the Eocene de- 

 posits of the Middle Atlantic Slope afford some important criteria for 

 the correlation of the strata. In the first place, the homogeneous nature 

 of the materials, already referred to, is a significant feature, and indi- 

 cates conditions imdisturbed by important physical changes throughout 

 the period of Eocene deposition. Again, the fact that the strata are so 

 largely composed of secondary materials shows that the position of 

 accumulation was in the vicinitv of a coast reached by no large sediment- 



