OLDER POTOMAC OF VIRGINIA AND MARYLAND. 521 



Nageiopsis zamioides Font 2 specimens. 



Platypterygium densinerve Font. ? 1 specimen. 



Quercophyllum tenuinerve Font. ? 1 specimen. 



Rogersia angustifolia Font. ? 5 specimens. 



Rogersia angustifolia parva Font. n. var 1 5 specimens. 



Rogersia longifolia Font 4 specimens. 



Saliciphyllum ellipticum Font 2 specimens. 



Sphenolepidium Sternbergianum densif olium Font 60 specimens. 



Thyrsopteris decurrens Font - . 1 specimen. 



Thyi-sopteris divaricata Font. ? 5 specimens. 



Thyi'sopteris insignis Font 15 specimens. 



Thyrsopteris nervosa Font 19 specimens. 



Thyrsopteris rarinervis Font 70 specimens. 



Zamiopsis insignis Font 2 specimens. 



Ctenopteris insignis Fontaine? 



PI. CXII. Fig. 7. 



1889. Ctenopteris insignis Font.: Potomac Flora (Monogr. U. S. Geol. Surv., Vol. 

 XV), p. 156, pi. Ixi, figs. 4, 4a, 5; pi. Ixii, figs. 1, la; pi. Ixiii, figs. 1, 2. 



Two specimens were found of a plant that agrees well with C. insignis, 

 a form that is highly characteristic of the strata of the Lower Potomac 

 of Virginia, on the horizon of the Fredericksburg beds. Although the 

 agreement is close, I hesitate to determine this plant positively as 

 C. insignis, for the amount of material is too small. PI. CXII, Fig. 7, 

 represents one of these specimens, and it is the terminal portion of an 

 ultimate pinna with several pinnules. It occurs in the collection made 

 by Prof essor Ward on May 11 and 17, 1897, the specimens found at the 

 two dates not being distinguished. 



Platypterygium densinerve Fontaine? 



PI. CXII, Fig. 8. 



1889. Platypterigiwn densinerve Font.: Potomac Flora (Monogr. U. S. Geol. Surv., 

 Vol. XV), p. 169, pi. XXX, fig. 8; pi. xxxi, figs. 1, 4; pi. xxxii; pi. xxxiii, 

 figs.l, la; pi. xxxiv, fig. 1; pi. xxxv, figs. 1, 2. 



A fragment of a large leaf was found at Langdon which is a species 

 of Platypterygium. It is shown in PI. CXII, Fig. 8. It contains a 

 portion of one side of the midrib, 4 cm. long. The greater part of the 

 width of the midrib is missing, so that its true size is not shown. To 



