166 THE POTOMAC OR YOUKGEE MESOZOIG FLORA. 



Zamiopsis petiolata, sp. nov. 



Plate LXVI, Fig. :!. 



Fi'ond bipinuate or tripiunate; principal rachis with a strong wing; 

 primary pinna terminating abruptly in a large incised pinnule similar to those 

 lower down ; pinnules petiolate, attached by the midnerve, prolonged into 

 a stout petiole, alternate, cut obliquely into oblong or subelliptical obtuse 

 pinnules, in the lower part of the ultimate pinnaj turned outwards. These 

 graduate in the upper parts of the same into lobes and teeth of the same 

 general character. The summit of the ultimate pinna is a broad oblong 

 segment ending in several shallow subacute teeth formed by the union of 

 the lobes at the summit ; the ultimate piiniie in passing towards the sum- 

 mit of the penultimate ones diminish much in size, the pinnules and lobes 

 passing finally into teeth ; lateral nerves in each pinnule and lobe consist- 

 ing of a nerve-bundle wliich goes off very obliquely from a point near the 

 lower end of the pinnule or lobe, branching near the insertion, and curv- 

 ing out to enter the pinnule or lobe, the branches forking again once or 

 twice, with the ultimate nerves very long and slender, owing to their deep 

 forking. 



Locality; Fredericksburg; very rare. 



This is anotlier of the peculiar cycad-like ferns which form such a 

 striking feature in the Potomac flora. Possibly it is a new genus, and I 

 place it with doubt provisionally in the genus Zamiopsis. The principal 

 i-achis has on each side a strong succulent wing or margin (see Fig. 3"). 

 The neiwes agree fully with those of Zamiopsis. 



PHANEROGAMS. 

 GYMNOSPERM^E. 



ZAMIEvE. 



The cycads of the Potomac flora, although presenting a considerable 

 number of species, by no means equal the Conifercc in that respect, but it 

 is especially in the number of individuals that this group contrasts with 

 the Coiiifcne. With the exception of Dioonifes the species, when found, 

 are among the great rarities at the different localities. As the specimens 



