DESCRIPTION OF THE SPECIES. 87 



ovate or rounded ol)loiig teeth wliicli are subacute to very obtuse ; nerves 

 in eacli lobe or tootli composed of a niidnerve wliicli sends oft' on eacli 

 side alternately l)ranclies which are single and arch upwards towards the 

 the summits of the lobes. 



Localities: Ilill-sido near Potomac Run ; fishing hut, above Dutch Gap 

 Canal ; rare at both localities. 



As this plant is found only rarely and in fragments, it is possible that 

 it may be identical with some other of the species described from the Poto- 

 mac formation. 



Pecopteris socialis, Hear. 



Plate XXI, Fig. 7. 



Leaf-substance thick and leathery ; principal racliis strong : pinnules, 

 or pinnju reduced to pinnules, subopposite to alteriuite, narrowed at the 

 base, and cut more or less deeply into ovate-acute to obtuse teeth; mid- 

 nerve of the pinnules, or reduced pinn;p, distinct ;• no lateral nerves in the 

 lobes and teeth visible, only a niidnerve. 



Locality: Bank near Brooke; rare. 



This plant is found rarely and in small fragments. Fig. 7 gives the 

 largest specimen found. Tiie detached ultimate pinna; given in this figure 

 agree quite well with tlie form given by Heer.' The only dift^erence is the 

 fact that in I leer's plant the pinnules, or reduced pinna-, are opposite. 

 This may well l)e the case with the Potomac plant, for the specimens 

 found belong to the uppermost and variable portions of the frond, which 

 often differ from the normal forms. 



Pecopteris angustipennis, sp. nov. 



Plato XXI, Fig. 10. 



Frond and primary pinnre unknown; pinnules, or reduced pinnae, 

 narrowly linear acute, cut obliquely into oblong or ovate-obtuse lobes or 

 pinnules; the pinnules or lobes containing each a niidnerve, sending oft" on 

 each side alternately straight, simple branches. 



Locality: Fishing hut above Dutch Gap Canal; very rare. 



' Flor. Fobs. Arc, vol. 6, Ft. II, PI. VII, Fig. 4. 



