72 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



des Arctisclien Zone, PI. XXVI, Fig. 7. The Potomac plant resembles 

 this a good deal. The form from Fredericksburg given in PI. IV, Fig. 

 2, is much like Neuropteris Ugafa,^ L. and H., but the nerves are more 

 copiously branched and the pinnules are broader. The Potomac plant is 

 no doubt nearer this latter than any other described form. 



Cladophlebis falcata, sp. nov. 



Plate IV, Fig. 8; Phito V, Figs. 1-6 ; Plate VI, Fig. 7; Plate VII, Figs. 1,2. 



Frond bipinnate or tripinnate, arborescent; racliis of the primary 

 pinnae or of the frond stout and rigid ; pinnae opposite, with a moderately 

 strong rigid rachis ; pinnules mostly opposite, sometimes alternate, falcate, 

 acute to obtuse, separate to the base, and slightly rounded off on the upper 

 side, with margins mostly entire, rarely slightly lobed, attached by the 

 whole of the broad base, varying in size according to position on the frond. 

 The pinnae of ultimate order, in ascending on the frond, pass through pin- 

 nules that are long and falcate with slightly lobed margins, into those of 

 smaller size wath entire margins; midnerve rigid and continued to near 

 the summit, with comparatively little diminution in size. The lateral 

 nerves are bifurcate and go off at an acute angle, and curve outwards to 

 meet the margin. 



Locality: Fredericksburg; not very rare. 



This fine plant is one of the most common ferns at Fredericksburg. 

 It has, more than is usual in the Cladophlebids, the aspect of an Alcthop- 

 teris, and although a good deal larger, is something like the Fecopteris Whit- 

 biensis of Lindley and Hutton. The Jurassic ferns that have some resem- 

 blance to this species are numerous, and it is hardly worth while to refer 

 to all of them, as none of them can with much probability be identified 

 with it. The forms with larger pinnules may be compared with Pecopteris 

 insignis, L. and H ,^ but, besides other points of difi'erence, the nervation is, 

 essentially distinct. 



Heer's Asplenium spectahUe, Flor. Foss. Arctica, Jura. Flor. Ost. Sib., 

 vol. 4, PI. XXI, Figs. 1, 2, has the nervation of this plant. The Potomac 

 specimens, with smaller pinnules, resemble more or less a number of 



' Foss. Flora of Great Britain, PI. LXIX. =Ibid., PI. CVI. 



