42 The Lower Ceetaceous Deposits oe Maeylanb 



starting point from the Old World geology, there will be no more ob- 

 jection to regarding the Potomac flora as Jurassic than there is now in 

 contemplating the Laramie flora as Cretaceous. In fact, so far as the 

 character of the flora is concerned, there is much less difficulty in the 

 case of the Potomac than in that of the Laramie, since, as I have shown, 

 the Potomac flora, viewed in all its bearings, cannot be said positively 

 to negative the reference of the formation to the Jurassic upon the evi- 

 dence of the plants alone. 



" I do not, however, desire to be understood as arguing for the Juras- 

 sic age of the Potomac formation. The most that it is intended to 

 claim is that, if the stratigraphical relations and the animal remains 

 shall finally require its reference to the Jurassic, the plants do not 

 present any serious obstacles to such reference.^' 



European paleobotanists having manifested much interest in the 

 Potomac flora, a statement was prepared by Professor Fontaine for Feist- 

 mantel, the celebrated Bohemian savant who made it the subject of a 

 paper which appeared in the proceedings of the Eoyal Bohemian Society 

 in 1889. This same year saw the appearance of Dr. Knowlton's long- 

 delayed work on the fossil wood and lignites of the Potomac formation, 

 a summary of which he had already contributed to the 1888 meeting 

 of the American Association for the Advancement of Science, an abstract 

 also appearing in the American Geologist. Professor Uhler also pub- 

 lished two additional papers at this time announcing the finding of his 

 Albirupean formation at Ft. Foote and on Piscataway Creek. 



In 1890 Professor Fontaine's Monograph was issue.d. In it are de- 

 scribed and illustrated 365 species, so called, of fossil plants, including 

 75 more or less nominal species of dicotyledons. The age is assumed to 

 be Neocomian, under which term are included the Wealden, Urgonian, 

 and Aptian groups of European geologists. 



In Professor Clark's account of the " Third Annual Geological Expe- 

 dition into Southern Maryland and Virginia," published in 1890, the 

 Albirupean is recognized as distinct from the underlying Potomac. The 

 same year N. H. Darton discussed the Potomac in a paper read before 

 the Geological Society of America, and the literature to date was passed 



