594 MESOZOIC FLORAS OF UNITED STATES. 



beds of Virginia. It contains absolutely no Jurassic or Older Mesozoic 

 species. 



The importance of the dicotyledons in any flora justifies a glance at 

 the table from this special point of view. The total number of dicotyle- 

 dons enumerated in the table is 48, of which 13 are new species. The 

 following 17 species occur in the District of Columbia and Maryland 

 exclusive of Hosiers Bluff: 



Protesephyllum Uhleri. 

 Quercophyllum tenuinerve ? 

 Rogersia angustifolia? 

 Rogersia angustifolia parva. 

 Rogersia longifolia. 

 Saliciphyllum ellipticum. 

 Vitiphyllum multifidum. 

 Vitiphyllum parvifolium. 



Celastrophyllum latifolium. 

 Celastropliyllum ? marylaiidicum. 

 Celastrophj'llum obovatum. 

 Ficophyllum tenuinerve ? 

 Menispermites tenuinervis. 

 Menispermites virginiensis. 

 Plantaginopsis marylandica. 

 ProtejEphjdlum dentatum. 

 Protesephyllum oblongifolium. 



Nine of these are found only at the Federal Hill locality and that 

 of Vinegar Hill, and this fact must be admitted to argue strongly for 

 the somewhat highei' position of these beds than that of the others in 

 Maryland exclusive of Rasiers Bluff. For my own part, notwithstanding 

 Professor Fontaine's reasoning, I am disposed to regard them as inter- 

 mediate between the Rappahannock and Brooke horizons, correspond- 

 ing somewhat to the position of the Mount Vernon beds, although for 

 some unknown reason there is scarcel}^ any resemblance between the 

 Mount Vernon and Federal Hill floras except that well-defined dico- 

 tyledons are abundant in both. The difference in the species may be 

 accounted for on geographical and topographical grounds, as one may 

 now select two places not widely separated at which quite different plants 

 are growing. 



There remain 8 species of dicotyledons occurring in the typical 

 Maryland beds. Of these Protece-phyllu7?i oblongifolium, Quei'cophyllum 

 tenuinerve % the three Rogersias, and Saliciphyllum ellipticum are all 

 found in the Langdon or Arlington beds. These certainl}' argue for 

 an age for these beds not lower than the Rappahannock of Virginia. 



The onlj' source that remains from which evidence of a lower position 

 for the Marjdand beds can be looked for is the new species found in them. 

 If these beds are really Jurassic and the bulk of the flora consists of Rap- 



