Maryland Geological Survey 45 



Geological Survey appeared. The Coastal Plain geology was contributed 

 by G. B. Shattuck;, that for the Potomac largely from Mr. Bibbins' notes. 

 The three Potomac formations present in that region, the Patuxent, 

 Patapsco, and Earitan, are delineated upon the large scale county map. 



In 1906 the Dover folio of the U. S. Geological Survey prepared by 

 Dr. B. L. Miller was published. This included a considerable area in 

 DelaAvare and northeastern Maryland, in which the Patapsco and Earitan 

 formations were described and mapped. 



Although it bears the date 1905 it was in 1906 that Ward's second 

 paper on the Status of the Mesozoic Floras of the United States was 

 issued. Over two hundred and fifty pages are devoted to the Potomac 

 flora of Maryland and Virginia, two additional species of Maryland 

 cycad trunks are described, and the large amount of material collected 

 by Mr. Bibbins for the Maryland Geological Survey and Goucher College 

 is discussed in the systematic part prepared by Professor Fontaine. The 

 correlations and stratigraphy are by Ward, who accepts the Maryland 

 Survey formational names for that State, uniting, however, the Patuxent 

 and Arundel formations. For Virginia the James Eiver and Eappahan- 

 nock are united and made the equivalent of the Patuxent and Arundel, 

 and the Mount Vernon and Brooke beds are correlated with the Patapsco 

 formation and an excellent map prepared by Mr. Bibbins shows the distri- 

 bution of the four formations of the Potomac Group in Maryland. Pro- 

 fessor Ward's final conclusion was that the whole Potomac Group is of 

 Cretaceous age, the older Potomac forming a part of the European 

 Wealden, which he regards as Cretaceous. The report on the Physical 

 Features of Maryland by Clark and Mathews, published this same year, 

 contained a new geological map of the State on which the different 

 Potomac members are shown, and the text contained a full description 

 and characterization of them. 



In 1907 the Patuxent Folio of the U. S. Geological Survey was pub- 

 lished by Shattuck, Miller and Bibbins. All the members of the Potomac 

 Group are fully described and mapped. 



In 1910 Berry published a short article in the Journal of Geology 

 showing that the Earitan formation was of Upper Cretaceous age. This 



