78 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



olate, acute, and falcate, narrowed at the base and decurrent, forming a 

 strong wing on the rachis, margins cut more or less deeply into ovate- 

 acute teeth ; miduerve slender, prolonged to near the summit of the pin- 

 nules; lateral nerves fasciculate in each tooth or lobe, forming nerve- 

 bundles, with mostly four branches. 



Locality : Fredericksburg ; very rare. 



This fine, well characterized plant is very rare, and, so far as known, 

 occurs only at Fredericksburg. It seems to have been a fern of large 

 size, and was probably arborescent. Some of the Potomac ferns else- 

 where described, such as CkulopliMns creiiata and Aspidhim Frederkks- 

 hiirgense, look a good deal like this plant, but the decided narrowing of the 

 pinnules on both sides at the base and the distinct wing in Cladopltlchis 

 alata serve to distinguish it. 



Geyler gives a figure' of his Pccopferis exiliformis, which in general 

 form looks something like the Potomac species, but the difi'erences are 

 marked. 



Cladopiilebis, sp. ? sp. nov. 



Plate XIX, Fig. 2. 



Frond and pinna; unknown; pinnules linear-lanceolate, acute, with 

 margins cut into ovate-acute lobes and teeth; midnerve as in the genus; 

 lateral nerves in each lobe or tooth having a midnerve, which sends off on 

 each side alternately branches that are mostly single, and curve upwards 

 towards the summit of the tooth. 



Locality: Near Telegraph Station. 



This plant is too fragmentary to make out its character. It may be 

 merely a portion of the upper part of the frond of some of the species 

 described under another name. The so-called pimiules look like pinniB 

 reduced to pinnules. 



Cladophlebis rotundata, sp. nov. 



Plate XX, Figs. 9, 10. 



Frond bipinnate or tripinnate, arborescent (?) ; principal rachis stout, 

 rounded, and prominent; pinnae short, with a strong rigid rachis; ultimate 



■ Foss. Ptlanzen Juraformation Japans, FaljBontograpliica, vol. 24, lci77, PI. XXX, Fig, 1». 



