594 :\IESOZOIC FLORAS OF UNITED STATES. 



beds of Virginia. Tl contains alisolutely no Jurassic or Older Mesozoic 



species. 



The importance of the cUcotyledons in any floi-a justifies a glance at 

 the table from this special point of view. The total mmiber 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: 



Protea>pliyllum Ililcri. 

 Quercophj'lluni temiinerve ? 

 Rogersia angustif olia ? 

 Rogersia angustifolia parva. 

 Rogersia longifolia. 

 Salicii)hyllum ellii)ticiim. 

 Vitiphyllum multifidum. 

 Vitipliylhim parvifoliuni. 



Celastrophyllum latifoliuin. 

 Celastrophyllum ( marylaiulicum. 

 Celastrophyllum obovatiim. 

 Ficophylium tenuinerve ? 

 Menispermites temiinervis. 

 Menispermites virginiensis. 

 Plantaginopsis marylandica. 

 Prote»phyllum dentatum. 

 Proteaephyllum 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 higher position of these beds than that of the others in 

 Maryland exclusive of Hosiers 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 ]\Iount Vernon beds, although for 

 some unknown reason there is scarcely 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 S species of dicotyledons occurring in the typical 

 Mar>dand beds. Of these ProtecephyUum oblongifolium, Quercophyllum 

 tenuinerve ?, the three Rogersias, and Saliciphyllum ellipiicum 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 only source that remains from which evidence of a lower position 

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

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



