152 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



locality. The leaf-substance of this plant is so thick and the epidermis so 

 well preserved that on drying the leaves curl up and peel off from the 

 stone like paper, so that it is difficult to preserve the specimens. The 

 nerves are seen with difficulty, but still they were clearly made out. Plate 

 XXVIII, Fig. 6, gives a portion lower on tlie frond than the part figured 

 in PI. XXIX, Fig. 1. Plate XXVIII, Fig. 2, gives a small form from 

 Fredericksburg with unusually remote pinnules. 



All the features of this plant, except the nerves, agree exactly witli 

 those given by Brongniart for Pacliyptcris lanceolata, and the resemblance to 

 Phillips's S2)he>i02)teris lanceolata is striking. 



This Potomac plant was evidently a large one. In tliis and the other 

 species of the genus found in the Potomac beds there is no tendency to 

 the lobing of the pinnules given by Saporta as existing on the anterior 

 margin of some species. 



SCLEROPTERIS ELLIPTICA, var. LONGIFOLIA, Sp. nOV. 

 PKite XXVIII, Fig. 7. 



Frond and pinnre not seen; pinnules linear-elliptical, alternate or 

 opposite, oblong-subacute, gradually narrowed towards the base, very 

 long, decurrent, forming a narrow wing ; leaf-substance leathery ; nerves 

 comparatively fine, closely placed, forking from a common nerve at the 

 base, diverging slightly, branches deeply once or twice forked, with the 

 ultimate branches parallel. 



Locality : Fredericksburg ; very rare. 



This is probably only a variety of Sderopteris ellijrfica, but the differ- 

 ences are considerable. The figure gives the summit of an ultimate pinna, 

 which ends in a pinnule larger than those immediately below it on the 

 pinna. It is noteworthy that the pinnules diminish very rapidly in passing 

 towards the tip of the pinna. 



SCLEROPTEEIS ViRGINICA, sp. nOV. 

 Plate XXVIII, Figs. 3, .5. 



Frond bipinnate or tripinnate ; rachises comparatively stout ; primary 

 pinnaj or those of the frond terminated by an ultimate piniiule like those 



