REVIEWS 311 



known deposits of the country. However, for nearly two generations 

 little has been done to extend our knowledge of these interesting beds. 

 Since the brilliant work of Rogers and Conrad ceased practically 

 nothing has been attempted in the way of keeping the information 

 regarding these strata abreast of the times. It is, then, with peculiar 

 pleasure that the recent revival of interest in these formations is noted ; 

 and none of the late contributions is more welcome than the one just 

 issued, on the Eocene of the Middle Atlantic region. 



The memoir contains a complete review of the literature and 

 results of past observations in this field. The author exhaustively 

 investigates both the stratigraphy and the fauna of this important 

 member of the coastal plain series. He traces the limits of the forma- 

 tion from its most northern occurrence in Delaware across Maryland 

 into Virginia, where it gradually becomes buried beneath later forma- 

 tions. 



A detailed study of the 300 feet of Eocene deposits in the central 

 portion of the district shows two distinct faunas, which are named the 

 Aquia Creek and the AVoodstock faunas, the former occupying a 

 sequence of beds extending some 60 feet from the base of the forma- 

 tion, while the latter apparently does not reach quite to its upper 

 limits. The Aquia Creek stage, which contains an assemblage of forms 

 closely allied to the middle Lignitic, probably stands, with its under- 

 lying poorly fossiliferous zone, as an equivalent, in a broad way, of the 

 whole of the Lignitic of the Gulf ; while the Woodstock stage, which 

 contains a group of forms closely allied to the Ostrea sellceforviis zone 

 of the Claiborne, stands, with the overlying and underl3ing beds, as 

 the equivalent, in a broad way, of the Buhrstoneand Claiborne, yet it is 

 not assumed that the lower and upper beds are exactly synchronous 

 with the lowest portions of the Lignitic and the highest portions of 

 the Claiborne. The much slower accumulation of the Atlantic coast 

 materials is shown in the fact that in Alabama more than 600 feet of 

 deposits are found between the two fossiliferous horizons above cited, 

 while in Maryland and Virginia a thickness of but little over 100 feet 

 is found, and without the differentiation into the fossiliferous zones 

 which characterizes the Gulf area. The middle Atlantic Slope Eocene, 

 therefore, represents, according to the author, only the Lignitic, Buhr- 

 stone, and Claiborne of the Alabama geologists. 



These results, together with others lately obtained in a study of the 

 Cretaceous strata throw much light upon the character of sedimentation 



