FOSSIL PLANTS. 399 



ascend to the border of the leaflets. This kind of nervation is that of Goppert's 

 species. But in our American specimens, the leaflets are broader, shorter, and 

 by the increasing depth of the divisions of the borders, they become by degrees 

 cut into lobes nearly to the base, and then are undistinguishable from Pecop- 

 teris unita, Brgt., except, perhaps, by the medial nerve or secondary rachis, 

 half round and not quite as thick, and by a thinner texture of the leaves. The 

 fructification is marginal, in round distinct sort which sometimes become irre- 

 gularly scattered by compression. 



GENUS PECOPTERIS, Brgt. 

 PECOPTERIS STRONGII, Sp. nov. 



PI. xiii, fig. 7-9. 



FROND simply pinnate or poly-pinnate, pinnge linear taper- 

 ing above to a point, slightly narrowing toward the base. 

 Pinnules alternate, perpendicular to the striated narrow ra- 

 chis, nearly one inch long and proportionately narrow, linear 

 obtuse, often slightly enlarged at the obtuse point, attached to 

 the rachis by their whole, sometimes enlarged base, discon- 

 nected and often distant, the distance, between them being 

 sometimes as wide as the breadth of the leaflets, becoming 

 closer to each other towards the point of the pinnae, where 

 they are shorter and connate at base. Fructification, marked 

 by scars of broad round sori, with a concave point in the cen- 

 tre, placed near the borders of the leaflets, close to each other, 

 ten to twelve on each side of the pinnules. Their place in re- 

 lation to the veins and veinlets is unknown, the substance of 

 the leaflets being thick, coreaceous, and the nervation obsolete. 



As it is seen in fig. 7 and 8, enlarged, the borders of the leaflets are slightly 

 undulate, an irregularity apparently caused by the compression of the sori ex- 

 panding the margin, or passing out of it, for in fig. 9 all the pinnules are en- 

 tire on the borders. This last specimen seems to represent a small frond ra- 

 ther than a pinna, for the leaflets turn downwards towards its base, as is the 

 case in some simple fronds of species of Poly podium of our time. By its form 



