86 THE POTOMAC OR YOUNGER MESOZOIG FLORA. 



Pecopteris constricta, sp. nov. 



Plate XX, FiRs. 1,2, C. 



Fi'ond bi pinnate or tripinnate, arborescent !; rachis of the primary pin- 

 nae or of the frond stout and rigid ; pinnjc alternate, with comparatively 

 stout and straight rachises ; pinnules with a thick and durable leaf-sub- 

 stance, opposite to alternate, narrowed at the base, and attached by tlie 

 central portions, those of the lower part of the frond cut deeply into ovate 

 acute lobes that are directed slightly forward, subfalcate, those of the mid- 

 dle portion of the frond oblong, acute, subfalcate, with ovate acute teeth, 

 the basal lower one being inserted in the angle between the main and sec- 

 ondary rachises ; midnerve distinct but slender, extending to the summit of 

 the pinnules ; upper pinnae narrowly linear, with ovate subfalcate pin- 

 nules united more or less at base ; lateral nerves in each lobe or tooth 

 composed of a midnerve, which sends off alternately on each side branches, 

 the lowest one of which on each side is forked ; the others are simple. 

 All the lateral nerves are very strong and prominent. 



Locality : Fredericksburg ; not uncommon. 



This handsome fern is very much like Bunker's Pecoptcris Browniana, 

 and it is even more like Pecopteris strictinervis, it being so close to the 

 latter that I have hesitated to separate them. The specimen shown in 

 Fig. 4 seems to be a portipn of a compound pinna which conies from the 

 upper part of a frond where the pinnae liave become greatly reduced, and 

 the large pinnules shown in Fig. 1, coming from the lower portion of the 

 frond, and in Fig. 2 from the middle part, are reduced to small ovate pin- 

 nules united at the base, and to ovate teeth. The lateral nerves in the 

 pinnules and lobes of this specimen are so distinct, that they look like 

 threads on the surface of the plant. 



Pecopteris brevipennis, sp. nov. 



Plate XXI, Figs. 1-3. 



Frond bipinnate or tripinnate, arborescent ? ; principal rachis stout 

 and rigid ; pinnules, or pinnaj reduced to pinnules, subopposite to alternate, 

 oblong, acute to obtuse at the tips, short, very uniform in length, cut into 



