OLDER POTOMAC OF VIRGINIA AND MARYLAND. 561 



street, near Federal Hill, lowest "vein" in Weaver's clay pit. The 

 rock matter carrying the imprint is different from that holding the 

 Acrostichopteris on Jackson street and indicates a different horizon. 

 It is not the friable sandy clay carrying Acrostichopteris, but a plastic 

 ash-gray clay, like some of that common in the Lower Potomac of 

 Virginia on the horizon of the Rappahannock or Fredericksburg strata. 



Seven specimens of N. angustifoUa occur in Mr. Bibbins's collec- 

 tions 7rom Federal Hill. One of these is a good imprint of a bit of a 

 penultimate twig, and the rest are fragments of ultimate twigs with 

 poor leaves. 



It is a noteworthy fact that this species of Nageiopsis in the Vir- 

 ginia Potomac shows generally much better preserved and more entire 

 forms than do the other species of this genus. 



Nageiopsis heterophylla Fontaine. 



PL CXVII, Fig. 6. 



1SS9. Nageiopsis heteroflvyUa Font.: Potomac. Flora (Monogr. U. S. Geol. Surv., 

 Vol. XV), p. 201, pi. Ixxxiv, fig. 4; pi. Ixxxvi, figs. 6, 6a, 7; pi. Ixxxviii, 

 figs. 2, 2a, 5. 



This species is represented in the Covington and Clement streets 

 collections by 4 specimens. One of these, occurring in collection No. 5, 

 is an imprint with a number of good leaves that are suddenly dimin- 

 ished in size toward the end of the twig. It is shown in PL CXVII 

 Fig. 6, and is W. C, B., No. 5987. While N. angustifoUa is more com- 

 mon in the upper or Aquia Creek portion of the Lower Potomac in 

 Virginia, this species is there confined to the lower portion of it. 



Genus PLANTAGINOPSIS Fontaine n. gen. 

 Characters of the type species described below. 



Plantaginopsis marylandica Fontaine n. sp. 



PI. CXVII, Fig. 7; PI. CXVIII, Figs. 1, 2. 



Among the specimens in collection No. 8, obtained at Covington 



and Clement streets, certain impressions are found, 5 in number, that 



seem different from any of the rest occurring here and which indicate 



the existence of a new genus and species. They occur sparingly and 



HON XLvin — 0.5- 



