OLDER POTOMAC OF VIRGINIA AND MARYLAND. 511 



Rogersia longifolia Font 4 specimens. 



Scleropteris elliptica Font 2 specimens. 



Sphenolepidium Sternbergianum densifolium Font 6 specimens. 



Sphenopteris latiloba Font. ? 2 specimens. 



Thja-soi^teris bella Font . 1 specimen. 



Thj^rsopteris crassinervis Font 9 specimens. 



Thyrsopteris decurrens Font 12 specimens. 



Thyrsopteris densifolia Font 4 specimens. 



Thyrsopteris divaricata Font 4 specimens. 



Thyi'sopteris nervosa Font 6 specimens. 



Thyrsopteris pinnatifida Font. 1 1 specimen. 



Zamiopsis insignis Font . 17 specimens. 



To obtain this variety of fossils only an imperfect exposure, partly 

 under water^ was available. No considerable amount of time was 

 devoted to collecting. No excavation was made and only the outcrop 

 as exposed was examined. 



Angiopteridium strictinerve Fontaine. 



PI. CX, Fig. 12. 



1889. Angiopteridium strictinerve Font.: Potomac Flora (Monogr. LT. S. Geol. Surv., 

 Vol. XV), p. 116, pi. xxix, figs. 8, 8a, 9. 



Only a single specimen of this plant was found on April 16, 1893, 

 consisting of the lower half of a pinnule from which the leaf substance 

 had disappeared, leaving the nervation distinctly impressed upon the 

 clay matrix. This is shown in PI. CX, Fig. 12. 



Cladophlebis falcata Fontaine. 



PI. CXI, Fig. 6. 



1889. CladopMehis falcata Font.: Potomac Flora (Monogr. U. S. Geol. Surv., Vol. 

 XV), p. 72, pi. iv, figs. 8, 8a; pi. v, figs. 1, la, 2-4, 4a, 5, 5a, 6, 6a. 



This plant also is rare. The best of the three specimens found is a 

 portion of an ultimate pinna with several well-preserved pinnules of the 

 largest size. It is shown in PI. CXI, Fig. 6, of this paper. 



