148 THE rOTOMAC OR YOONGEIl MESOZOIC FLORA. 



which diverges liabelhitely from u more or less i)roiiounced midnerve, the 

 branches usually once forked, rarely bifurcate. 



Locality : Hill-side near Potomac Run ; comparatively rare. 



This plant is much iliore rare than the type species, and, although 

 evidently nearly allied to it, has the nerves more widely diverging and 

 remote, a more regular dentation, a winged rachis in the ultimate pinnae, 

 and wider, more rounded lobes. The pinnules also are decidedly broader 

 in proportion to their length. 



SAGENOPTERIS, Pr. 



The Jurassic genus Safjeno2)teris is represented in the Potomac flora 

 by several well-characterized species. None of these, however, seem to 

 be very abundant, and the genus furnishes a very small element to' the 

 flora. 



Sagenopteris latifolia, sp. nov. 



Plate XXVII, Fig. 10. 



Frond unknown ; pinnules apparently subquadrilateral, narrowed 

 o-radually to the base and rapidly to the summit ; midnerve in the lower 

 part of the pinnule strong, in the upper part dissolving into branches ; 

 lateral nerves going off very obliquely, branching near the midrib, turning 

 outward, and then by repeated branching and anastomosis forming long, 

 rather regular, elliptical to rhombic meshes, which fill the lamina. 



Locality : Near Telegraph Station. 



Only two fragments of this plant were found. As, however, no 

 detailed exhaustive search was made at this locality, and the amount of 

 material was small, the rarity may be apparent rather than real. The 

 shape of the pinnules is nearer that of S. rhoifolia of the Rhetic than that 

 of any other species of the genus known, but the anastomosis is more 

 copious than that of the Rhetic species. In copiousness of anastomosis 

 and in the shape of the ine.slies it is nearer S. MantelU Schenk, of the 

 Wealden. It seems to lie between these two species. In the figure the 

 margin on the right-hand side appears to represent the original border of 

 the leaf, but the other parts have been torn away. 



