88 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



The true character of this plant can not be made out until more and 

 better specimens are found. It has some resemblance to Pecopteris ovato- 

 deniata, and may possibly be tlie same with that fern. 



Pecopteris Browniaxa, Dunker. 



PLateXXII, Figs. 10, U; Plate XXIII, Figs. 2-7; Plate XXVI, Figs. 3,13. 



Pecopteris Browniana, Dnnker, Monograph, PI. VIII, Fig. 7. 



Alethopleris Bronniana, Scbimper, Traite, III, p. 503. 



Pecopteris Browniana, Scheuk, Foss. Flor. Nortlw. Weald., PI. V, Figs. 2, 2>. 



Ahthopieris Browniana, Schenk, Foss. Flor. Nordw. Weald., PI. XXVI, Figs. 3-5. 



Frond tripinnate, arborescent; the rachises of different orders are 

 comparatively stout and rigid; ultimate pinnae short, subopposite or oppo- 

 site, linear, acute; pinnules varying considerably in different parts of the 

 frond, usually quite small, in shape oblong-obtuse to subacute; separate at 

 base in the lower portions of the frond, united slightly in the upper por- 

 tions, generally separate; in the upper part of the frond the pinnse reduced 

 to pinnules, either toothed or with entire margins, the former much nar- 

 rowed at base, forming a sort of petiole. 



Localities : Fredericksburg ; Baltimore, among the plants collected by 

 Meek, and at Covington street ; red clay ball in the banks of Dutch Gap 

 Canal ; hill-side near Potomac River; 72d mile-post, near Brooke. 



This elegant little plant is one of the most widely diffused ferns of the 

 Potomac formation. It is at the same time quite well preserved in the 

 specimens found, hence the different parts can be made out pretty well. 

 It being thus fully represented, some of the specimens differ somewhat 

 from the European forms of the Wealden. Tlie drawing, PL XXII, Fig. 

 11, is from a specimen collected by Mr. Meek. The nerves of this species, 

 although not strong, are very distinct. 



Pecopteris pachyphylla, sp. nov. 



Plate XXVI, Figs. 4,5. 



Frond bipinnate or tripinnate ; rachis in pinna3 of all orders, com- 

 paratively stout and rigid; ultimate pinnae in the lower part of the frond 

 linear, in the upper part oblong-lanceolate; all alternate; pinnules very 

 small, oblong, very obtuse, subopposite, slightly falcate, united at base to 



