OLDEH POTOMAC OF VIIUITNIA AND :\IAHYLANn. 521 



Nageiojisis zaminidcs Font 2 siK'cimciis. 



Platv])tprvgiiini dcnsincrve Font. ? .. 1 speciincn. 



QueiTophylluni tciminorvo Font. I 1 spcfinion. 



Rogersia angust il'olia Font. ? 5 specimens. 



Rogersia angustifolia parvaFont. n. var 5 specimens. 



Rogersia longifolia Font 4 specimens. 



Salicipliylium eilipticum Font 2 specimens. 



Spheniilepidiiim .Sieiiihergianum densifolium Font . _ 60 specimens. 



Tliyrsojjteris decurrens Font- 1 specimen. 



Tliyrsopteris divaricata Font. ? 5 specimens. 



Thyrsopteris insignis Font , .15 specimens. 



Tliyrsopteris nervosa Font.. 19 specimens. 



Tliyrso])teris 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. 1.56, pi. Ixi, figs. 4, 4a, 5; pi. Ixii, figs. 1, la; pi. Ixiii, figs. 1, 2. 



Two speeinioiis were fouiul of a plant that agrees well with C. insignis, 

 a form tliat 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 Professor Ward on May 11 and 17, 1897, the specimens found at the 

 two dates not being distinguished. 



Platypteryoium densinerve Fontaine? 



PI. CXII, Fig. 8. 



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

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

 figs.l, la; J)!, xxxiv, fig. 1; pl. xxxv, figs. 1, 2. 



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

 of Platypterj-gium. It is shown in Pl. 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 



