FLORA OF OLDKR POTOMAC FORMATION. 389 



and May 2;>, 1,S<)4. and was fully disciiss(>d by all the geologists who had 

 studied the formation. 



Mr. W J Mc( ;oo road a paper before the International Geological 

 Congress, at its meeting in Washington in 1891, the publication of which 

 was delayed until sometime in 1894." in which liie Potomac formation 

 is treated among the rest that make up the geology of Washiugtoii. In 

 this paper (p. 238) he extends the formation to include' the latei' hods of 

 New Jersey (Raritan foi'malioii) and the South (Tuscaloo.sa formation), 

 but he does not indicate whether he considers these hods later in depo- 

 sition than those of Virginia. In saying that Professor Fontaine regards 

 the Potomac as "probably equivalent to the Cenomanian of Evu'ope," 

 the word "Cenomanian" is probably an eiror for Neocomian. 



Field work in the Potomac of Maryland was actively prosecuted hy 

 Mr. Bibbins and myself until the end of July, 1894. There wei'o several 

 reports of finding impressions of ferns and other plants in the iron-ore 

 region, especially on the Bannon estate at the Kill)ern ore bank. One 

 of these fern leaves had attracted special attention and was traced to 

 persons in Towson, where it had been sent, but all efforts to find it failed. 

 Mr. Bibbins followed uj) all these indications with great persistence, and 

 at last, on July 17, he succeeded in finding a spot on the above-mentioned 

 estate where plant impressions occur in the iron-ore beds. He imme- 

 diately reported the fact to me, and in his letter, dated July 18, 1894, says: 



This ore is very different from any other brown ore I ever saw. It is raised 

 either as ore or paint, and is obtained near the surface by "gougini^." I secured a 

 dozen of the lumps and upon breaking them open found tliat tliey were full of 

 plant remains, and that some of the leaves were very perfectly preserved. Fern 

 leaves were among the species found. 



He sent me a few specimens, .which I examined and reported on to 

 him as follows, under date of July 20: 



I can identify at least one species, viz, Cladophlebifi acuta Font., thus far only 

 found in the Rappahannock series. I tlunk you have also Dryopteris fredericks- 

 hurgense Font., found in l)oth the Ra])piihannock and the James River series, and 

 also in the Kootanie of the West. We begin to know now where to look for plants 

 in the iron-ore rejiion; they arc right among the ore. Tlie little fragment I got at 



" Geology of Washington and vicinity, by W J McGce, with the collaboration of G. H. Williams, Bailoy 

 Willis, and X. II. Daitoii: Compto-Kcndu dc la .5"" Session dii CongrOs Gi^ologique International, Washington 

 189), Washington, 189.3, pp. 219-2.51. 



