DESCRIPTION OF TllK SPECIES. 99 



The line specimens depicted in IM. XVII, Fio-. 1, and PI. XVI, Fijr. 3, 

 come from the entrance to Trent's Reach. The latter seems to be the 

 upper part of a compound pinna. The sori are comparatively large. 

 Nerves occur on all of the pinnules. They are most numerous on the 

 pinnules near tlie base of the ultimate pinna% and are not present at all on 

 the pimudes towards the end of tlie.se pinn;i3. A noteworthy feature of 

 the fructified pinnules is the fact that the l)asal ones are shorter and smaller 

 than those towards the middle of the ultimate pinuiv. In this feature, 

 and in the opposition of the ultimate pinnie, the fertile form differs from 

 the sterile one. The plant seems to be not near any described form. It is 

 more like Aspldium Jciiscni Heer, than any other. 



ASPIDIUM CYSTOPTEHOIDES, sp. UOV. 

 Plate XVI, Pis- 2. 



Sterile fronds not seen; racliis of ultimate pinna; slender; pinnules 

 alternate, attached b}' the middle portion of the base, crenately toothed, 

 obtuse; sori ratlier large, in two rows, one on each side of the midrib, 

 placed near the margin, on the summit of the uppermost branch of the 

 nerves; subglobose in shape, similar to those of Cijsti)pteris, with an inflated 

 indusiumatba.se; nerves branching palmately in each tooth. 



Locality : Fredericksburg. 



This pretty fern is very rare at Fredericksburg. It is much like the 

 genus Cysfopfcris of the Aspidcce. It does not seem to be nearly allied to 

 any described fossil. 



AspiDiuM Oerstedi ? Heer. 



Plate XIX, V\'i. 4. 

 (See Heer, Plor. Foss. Arctica, vol. (i, Part 'J, Foss. Flor. GWiii lands, p. 30; vol. 7, p. 2.) 



Pinnules narrowly linear, acute, with minute teeth directed forwards; 

 nerves simple, parallel and ending in the teeth. 



Locality : Near Telegraph Station. 



This plant, although found in only one small fragment, is quite distinct 

 from all others of the Potomac flora. I unite it with Ileer's ])lant provision- 

 ally and with doubt, as the fragment is too small to give the full character 



