372 MESOZOIC FLORAS OF UNITED STATES. 



Knowlton had read at the Cleveland meetmg of the American Association 

 for the Advancement of Science, 1888, a summary of his results, an 

 abstract of which was published in the proceedings," and also in the 

 American Geologist.* 



Professor Uhler published another paper during 1889,'' which, 

 though chieflj^ devoted to the description of Eocene shells, discusses the 

 geological relations of the Cretaceous beds and finds the Albirupean in 

 the bluffs below Fort Foote, on the Potomac, overlying the beds which, a 

 few hundred yards above, viz, at Rosiers Bluff, have yielded a large flora 

 belonging to the Aquia Creek series or upper horizon of the Older Potomac. 

 In a later paper'' he gives a section on Piscataway Creek showing the 

 same beds (pp. 103-104). 



Prof. William B. Clark, in his account of the "Third Annual Geological 

 Expedition into Southern Maryland and Virginia,'" recognizes Uhler's 

 Albirupean as distinct from the underlying Potomac. 



Mr. N. H. Darton had been for some time engaged on the areal 

 geology of the District of Columbia and parts of Maryland and Virginia 

 in which the Potomac formation occurs. He did not cooperate with the 

 paleontologists, nor, so far as I am aware, consult them, but he accepted 

 the name Potomac formation, which he did not further subdivide in 

 coloring his maps. He read a paper before the Geological Society of 

 America at its meeting in December, 1890, on the general geology of this 

 region,'' in which he named and described the overlying marine deposits 

 (Severn, Pamunkey, Chesapeake) and discussed the Potomac, but added 

 nothing to the knowledge of it that had been gained by others. 



At my request, Professor Fontaine undertook the determination of 

 the plants described by R. C. Taylor in 1835 (see pp. 344-345) 

 from the figures given on his plate, and he communicated the results to 

 me in a letter dated May 17, 1891. As this paper was overlooked by 

 him in preparing his monograph, and no one has attempted to determine 



<i Vol. XXXVII, Salem, 1889, pp. 207-208. " 



I' Vol. Ill, No. 2, February, 1889, pp. 99-106. 



c Additions to observations on the Cretaceous and Eocene formations of Mar_vland, by P. R. Uhler: Trans. 

 Maryland Acad. Sci., Vol. I, pp. 4.5-72. 



(' Notes and illustrations to "Observations on the Cretaceous and Eocene formations of Maryland:" Ibid. 

 June 7, 1890, pp. 97-104, pi. A. 



f Johns Hopkins University Circulars, Vol. IX, No. 81, May, 1890, pp. 69-71. 



./ Mesozoic and Cenozoic formations of eastern Virginia and Maryland, by N. H. Darton: Bull. Geol. Soc. 

 Am., Vol. II, April 14, 1891. pp. 431-4.50, pi. xvi. 



