DESCRIPTION OF THE SPECIES. ' 71 



This plant is plainly Jurassic in type, and may be regarded as a sur- 

 vivor of the Jurassic flora. It is so much like the sterile forms of the plant 

 from the older Mesozoic or llli:vtic flora of Virginia, first made known by 

 Bunbury and described by me in Contributions to the Knowledge of the 

 Older Mesozoic Flora of N'irginia,^ under the name A eras tick ides Jinmc- 

 ccfoUiis, that one is tempted to consider it as a descondant of tlie latter. 

 Comparison may be made witli PI. VII, Fig. 1, and I'l. \'lll. Fig. 1, of 

 tlie work cited. It is also in sonu' points nuu'h like Acro-^tichidcs rhoinhi- 

 folhis, described in the same monograph. 



The Potomac plant is strikingly like Brongniart's Pecopferis Wliit- 

 hiensis, and P. tenuis, and one may well hesitate to separate them. Ileer, 

 in Flor. Foss. Arctica, vol. 4, under the name Asplcniam, has described 

 some forms that are very close to the plant now in ipiestion. It does not, 

 however, seem proper to make the Potomac plant an Asplenlum so long as 

 it shows no fructification. 



Clauophleius dknticulata, sp. nov. 



Plato IV, Fij;. 2; PLate VII, Kig. 7. 



Frond bipiiuiate or tripinnate ; rachis of tlie pinna' rather slender ; 

 pinnules opposite to alternate, attached by the entire Ijase, oblong to lance- 

 olate, subfalcate, minutely dentate toward their tips, those in the upper 

 part of the frond entire ; midnerve as in the genus ; lateral nerves bifur- 

 cate or simply forked, and rather slender. 



Localities: Fredericksburg; i-oad-side near Potomac Kun; very rare. 



I have witli mucli hesitation united tlie plant given in PI. IV, Y\^. 

 2, which comes from Fredericksburg, and that depicted in PI. VII, Fig. 

 7, which was found on the road-side near Potomac Run. The latter dif- 

 fers from the former in having tlie piniuiles more erect, oljlong in shape, 

 and sei)arate to the l)ase. Then, too, they have their nerves simply forked, 

 and more Pecoptcris-like. The very fragmentary nature of the specimens 

 does not permit the true nature of the species to be fully made out. 



The form given in PI. VII, Fig. 7, may be compared with I'ccopteris 

 denticulata, Heer, as given in Flor. Foss. Arctica, vol. 3, Die Kreideflora 



I U. S. Geol. Survey, Mou. No. 6, 1883. 



