380 PALAEONTOLOGY OF ILLINOIS. 



fossiliferous limestone, whose characters are so much like those of the Penna. 

 black limestone seen at the top of the millstone grit with Caulerpites margi- 

 natus, Lesqx., Jour. Am. Phil. Soc., vol. 13, p. 313, occupies the same level. 

 This is a peculiar coincidence of a singular formation, which, exceptionally in 

 the flora of the Coal Measures contains Fucoides, in both the coal basins of 

 Penna. and of Illinois. 



FRONDS AND BRANCHES OF FERNS, 



GENUS NEUROPTERIS, Brgt. 



This genus, limited as it is, vol. ii, p. 427 of this Eeport contains some spe- 

 cies, whose leaflets, more generally round, have no distinct medial nerve, and 

 which, from this peculiarity of form and nervation, are referable to the genus 

 Nephropteris, Brgt., already a modification or subdivision of the genus Oy- 

 clopteris, of the same author. As some of our species are represented, even 

 on the same specimens, by fronds bearing both oblong leaflets with a well 

 marked medial nerve, and nearly round ones without it; or by branches bear- 

 ing round or polyform. pinnules with a definite medial nerve, and oblong ones 

 without a trace of it, the subdivision of the genus Neuropteris is as difficult as 

 it is inconvenient, with the materials now at hand. This opinion is further 

 supported by the descriptions and figures of some of our species. 



NEUROPTERIS HIRSUTA, Lesqx. 



Boston Jour, of Nat. Hist., 1854; State Geol. Rept. of Penna., p. 857, PI. iii, 6/, PI. iv, 

 fig. 1 to 16, excl. syn. 



The degree of relation of this species with Neuropteris cordata, Brgt., is not 

 yet ascertained. In his admirable work on the Fossil Flora of the Permian 

 (1864-65) p. 100, PI. xi, fig. 1 and 2, Prof. G-oppert has published as Neurop- 

 teris cordata, Brgt., part of a pinna, bearing on one side of its broad rachis a 

 series of alternate, oblong, cordate, obtuse leaflets, one inch broad, four inches 

 long, marked with a thick medial nerve, and on the other side diminutive leaf- 

 lets, very short and enlarged, resembling, according to the author's remarks, 

 some of those of the polymorphous Neuropteris auriculata, Brgt. If the true 

 Neuropteris cordata has such leaflets of various forms alternately attached to a 



