84 TOE POTOMAC OR YOUNGEll MESOZOIG FLORA. 



Tliis plant is more like Fecoptcris denticulata,^ Brong., than any other. 

 The only difference is found in the more slender and elongated pinnules 

 of the Potoinac fossil and in their greater thinness. Pteris fri(jida," Heer, 

 from the Atane beds, resembles the Potomac plant, but it lacks the distinct 

 toothing found in the latter. 



Pecopteris Steictinervis, sp. nov. 



Plate XIII, Figs. 6-8 ; Plate XIX, Fig. 9 ; Plate XX, Fig. 3 ; Plate XXII, Fig. 13; Plate CLXX, Figs. 5, 6. 



Frond bipinnatifid or tripinnatifid; rachises slender; pinnae suboppo- 

 site to alternate, linear; pinnule.s united for a considerable distance above 

 their bases, oblong, usually obtuse and inclined forward, slightly falcate, 

 those of the lower part of the frond denticulate, of the upper part entii'e; 

 leaf-substance thick and obscuring the nerves, which are slender and im- 

 mersed in it; lateral nerves of the lower pinnules furcate, with the lower 

 branch ending in the teeth ; lateral nerves of the upjier pinnules mostly 

 forked only in the basal ones, most of them simple, all usually parallel 

 and straight, or nearly so. 



Localities: Fredericksburg; Covington street, Baltimore; rare. 



This elegant little plant occurs more abundantly at Fredericksburg 

 than at Baltimore. All the specimens figured, e.Kcept PI. CLXX, Figs. .5, 

 6, come from the former place. Still it is not an abundant plant even 

 there. PI. XIII, Fig. 6, seems to be an abnormal form, which has the 

 pinnules united higher up than usual and the lateral nerves more commonly 

 forked and more curving than is usual in the pinnules of this fern, which 

 -have entire margins. Perhaps it would be better to separate thi.s' as a 

 variety with the name var. imita. PI. XIII, Fig. 7, gives a noi'mal form 

 for the pinnre and pinnules coming from the middle part of the frond. 

 Fig. 8 of the same plate seems to come from down lower on the frond, 

 where the toothing is more distinct and the nervation is all forked. PL 

 XIX, Fig. 9, is a normal form for the parts belonging to the upper portion 

 of the frond. 



This plant is very much like Pecopteris Browniana, Dunker, of the 

 Wealden of Germany, as figured by Schenk in Foss. Flor. Nordw. Weald- 



iHist. V^g.,Pl. XCVIII, Figs. I, 2. 2 Flor. Foss. kxc, vol. 6, PI. X, Figs. 1-4; PI. XI, etc. 



