254 Systematic Paleontology 



hertsii. The additional fragments of Potomac ferns which are referred 

 to this species are not common and are equally unimportant botanically 

 and stratigraphically. The two CladopTilehis sp., Fontaine, are clearly 

 enough referable to this species. Cladoplilebis pachyphylla is considered 

 as an anomalous pinna with thicker more remote pinnules, which are 

 contracted at the base. It was founded on a single fragment from Fred- 

 ericksburg, Virginia, and if not an example of this species is simply a 

 distal aberrant pinna of one of the other described species from that 

 locality. The specimen which was the basis for the presence of Aspidium 

 cerstedi Heer in this flora is the merest fragment without significance in 

 any way. 



The fertile pinnse of CladopMebis Alhertsii agree with those of Cla- 

 dophlehis parva and other Potomac species in the general character, form, 

 and arrangement of the sori, the nature of the material precluding any 

 more detailed information on this point. The sori appear to be confined 

 to the basal part of the proximal pinnules. The present species is closely 

 related to the contemporaneous form CladopMebis virginiensis Fontaine. 



It is common in the Wealden of England and Germany, and probably 

 in homotaxial or somewhat younger beds in Austria and Eussia. It has 

 been recorded from the Cenomanian of Bohemia and from the Atane 

 beds of Greenland, but both of these determinations may be considered 

 as very doubtful. Nathorst has described a similar form from Spitz- 

 bergen as Cladoplilebis sp. A.^ In this country it is definitely known only 

 from the Potomac Group. It has been recorded from the Patapsco for- 

 mation at Vinegar Hill, Maryland, but the single specimen is referred 

 by the writer to CladopMebis virginiensis, which is abundant at this 

 locality. 



Occurrence. — Patuxent Formation. Potomac Eun, Telegraph Sta- 

 tion (Lorton), Dutch Gap, Trents Eeach, Fredericksburg, Virginia. 

 Arundel Formation. Arlington, Hanover, Bay View, Maryland. 



Collections.— J] . S. National Museum, Goueher College. 



^ Nathorst, Kgl. Svenska Vetens.-Akad. Handl., Band xxx. No. 1, 1897, p. 49, 

 pi. ii, figs. 9, 11-13. 



