DESCIUI'TION OF THE Si'EClES. 113 



Angioptekidium, Schiniper. 



Frond simply pinnate; pinnules long-, linear, more or less narrowed 

 towards their ends, roundeil at the base or nearly heart-sluiped, attached 

 to the principal rachis l)y the niidnerve alone, which sometimes forms a 

 disarticulatin<>- siiort pedicel; midnerve strong, lateral nerves going off 

 oblitpiely and abruptly, taking a horizontal ))osition f)r l)ent somewhat 

 obliquely upwards, simple and forked. 



This description given by Schimper' agrees exactly with a niuiiber of 

 species found in the Potomac fli>ra. An(jioj)ti'rld'tum is a characteristic 

 Jurassic type, and the number of species of this genus occurring in the 

 Potomac flora adds decidedly to the Jurassic element otherwise so strongly 

 represented in this flora. 



Angioptekidium auriculatum, sp. nov. 



Plate VII, Figs. 8-11 ; Plate XXVUI, Fi^. 1. 



Frond pinnate; pinnules thick and leathery, long linear, subacute, 

 remotely placed, free to the base, auriculate at base, attached by the mid- 

 rib alone; auricles of the bases of the pinnules overlapping the upper .sur- 

 face more or less ; midrib of pinnules rather stout and rigid; lateral nerves 

 often obscurely shown, fasciculate or bifurcate, and towards the tips simpl)- 

 forked. 



Localities: Fredericksburg; road-side near Potomac Run ; rare. 



The plant is rare at each locality, but is most common at Fredericks 

 burg. It is something like Ptcrh longipennis Heer,^ but there is no reason 

 to think that it is a Ptcris. It resembles Pccopteris salicifoUa,'* Oldhain and 

 Morris. The forms figured in Figs. 8, 9, 11 occur at Fredericksburg-; 

 Fig. 10 occurs at the locality near Potomac Run. This is different from 

 the others in the great length of the pinnules and in the fasciculate nerves, 

 which are bifurcate, with the branches again forking near their tips. The 

 nerves are obscure on the upper surface of the pinnules. The main rachis 

 is stout and keeled on the under surface, as is shown in Fig. 9. On the 



' Zittel's Hand-book, vol. 2, p. 134. 



"Foss. Flor. Arc, vol. 6, pt. 2, PI. X, Fig.s. 5-13. 



'Foss. Flora of the Rnjin.-ihal series, PI. XXVII, Fig. 2. 



MON XV 8 



