FOSSIL PLANTS. 403 



PECOPTERIS ELEGANS, Germ. 

 Polypodites elegans, Gopp., Syst., p. 344. 



PL xv, fig. 10. 



We have in abundance, in the concretions of Mazon creek, specimens which 

 agree in every point with the figures and description of this species. Pin- 

 nae, bearing linear leaflets, entire on the borders, round at the top, marked 

 by medial nerves from which branch in an acute angle simple veins, ascending 

 straight to the borders, or sometimes slightly curving upwards. But the 

 characters here indicated are so variable and passing by such inappreciable 

 transitions to those of the true Pecopteris unita, Brgt., that after the examina- 

 tion of many hundred specimens, it is impossible to point out a single trait 

 which could be described as distinctive of one of these species. I therefore 

 consider this Pecopteris elegans, Germ., as a variety of Pecopteris imita, Brgt. 



PECOPTERIS ASPIDIOIDES, Brgt., Veg. foss., p. 311. 



PI. 112, fig 2. 

 Found at Mazon creek ; rare ; seen only in two specimens. 



PECOPTERIS ABBREVIATA, Brgt., Veg. foss., p. 337. 



PL 115, fig. 1 to 4. 



Numerous and very fine specimens in concretions from Mazon creek are 

 referable to this species, rather by the figures given of it by Geinitz in his 

 Versteinerimgen, than to those of Brongniart. The secondary pinnae are short, 

 all equal, the veins and veinlets much inflated, the pinnules more generally 

 disconnected f. c. f. It is altogether a different species from Pecopteris Miltoni 

 Brgt., to which the German author unites it as a variety, at least, if we con- 

 sider our American specimens identical, which, however, may represent a new 

 species. 



