OLDER POTOMAC OF VIRGINIA AND MARYLAND. 553 



the Woman's College of Baltimore. This fern is the most abundant 

 fossil in the collection made by Professor Ward and Mr. Bibbins. P. 

 virginiensis has a character which, even in small specimens, may be 

 ea^ly distinguished. It is widely distributed both areally and vertically 

 in the Lower Potomac formation of Virginia, being found in the highest 

 and the lowest beds. It is most common at the Virginia locality "Road- 

 side near Potomac Run," on the Fredericksburg or Rappahannock 



horizon. 



Selaginella marylandica Fontaine n. sp. 



PL CXV, Figs. 9, 10. 



The specimen found at the Vinegar Hill locality of this new species 

 of Selaginella is quite distinctl}' preserved, so as to show its character 

 well. The parts shown are several small fragments of penultimate twigs. 

 The penultimate branch forks in a dichotomous manner sympodially, 

 one branch in the forking being- more developed than the other and con- 

 tinuing the twig, giving renewed branching. The minor branch in each 

 case becomes an ultimate one. The longest of the penultimate twigs is 

 only 12 mm. long, while the width, including the leaves, is only 2 mm. 

 The leaves shown are minute in size, arranged in two rows, expanded in 

 the same plane, and lateraUy attached. No leaves show on the upper 

 surface, perhaps because they were carried away in splitting the shale. 

 The lateral nerves are leathery in texture and well preserved. They 

 have a distinct midnerve and are attached by a narrowed portion of the 

 base. They are slightly cordate at base and are widest near the base. 

 In general form they are ovate-acuminate and terminate with a well- 

 preserved awn. The leaves are sometimes slightly falcate. The speci- 

 men is shown natural size in PI. CXV, Fig. 9, and enlarged three diame- 

 ters in Fig. 10. It was collected by Mr. Bibbins in October, 1895, and 

 is No. 6148 of the Woman's College. 



ViTiPHYLLUM MULTiFiDUM Fontaine. 



PI. CXIX, Fig. 5. 



1889. VitifliyThwrn multifidwm Font.: Potomac Flora (Monogr. U. S. Geol. Surv., 

 Vol. XV), p. 309, pi. clxxxii, figs. 1-9. 



As above remarked, this specimen, the only one found at Vinegar 

 Hill, occurs on the same piece of shale as the Celastrojyhyllum obovatum. 

 It is noteworthy as being the only case of the occurrence of this species 



