OLDER POTOMAC OF VIRGINIA AND MARYLAND. 477 



States Geological Survey. Since that time a large amount of material 

 has. been obtained from these beds. Most of the plants furnishing the 

 basis for the results given in that work were secured from localities in 

 Virginia. In the collections made later a very large proportion of the 

 fossils come from Maryland, being secured for the most part by Mr. 

 Arthur Bibbins, of the Woman's College of Baltimore, and by the Mary- 

 land Geological Survey. A good many specimens have been secured by 

 Professor Ward from a new horizon, not known at the time of the publi- 

 cation of Monograph XV. The strata yielding these plants have been 

 named by Professor Ward the Mount Vernon series. Professor Ward 

 and others have also made considerable collections from Fort Foote, on 

 the Maryland side of the Potomac River, from the excavation for the 

 new reservoir at Washington, and from various other localities in Mary- 

 land, the District of Columbia, and Virginia. 



All of these collections have been turned over to me for study and 

 description, in order that the publication of data relating to the fossil 

 flora of the Lower Potomac of the Atlantic States raay be brought up to 

 date. The object of the present paper is to give the result of such study. 

 By far the greater part of this material, obtained since the publication 

 of Monograph XV, is composed of species described in that work. Some 

 of the collections were made from new horizons or from those whose 

 relations to the horizons yielding the plants there described are unknown. 

 Many of them are from localities remote from one another, so that the 

 territory occupied by the Lower Potomac flora of the Atlantic States is 

 now much more full}' represented by fossil plants than it was at the time 

 of the publication of Monograph XV. It is surprising to find so few new 

 species represented in this large additional supply of material. 



In dealing with this more recenth' obtained matter, in order that it 

 may serve to determine the geological horizons from which the plants were 

 obtained, it seems best to take up the collections separately and compare 

 the plants in them with those from the horizons and localities described 

 in Monograph XV. The few new forms that have been found will be 

 described and figured in their proper places. Where good specimens of 

 previously described species are obtained they will be figured in some 

 cases, for the sake of comparison. 



The collections have very unequal value, owing to difference in their 

 size and in the perfection of preservation of the impressions. In 



