DESCKIPTION OF SPECIES. PP. 73 



given the name to the species. The intermingling of fertile 

 and sterile pinnules is a rare feature. 



Habitat. — Roof-shales of the Waynesburg Coal, Cass- 

 ville, W. Va. 



Pecopteris rotundifolia, Sp. nov., PI. XXIV, Fig. 6. 



(Frond, tripinnate; primary pinnse, lanceolate in outline, 

 with a slender and somewhat tiexuoiis rachis : secondary 

 j)innfe, linear, alternate, and going off at nearly a right 

 angle, with slender rachis ; pinnules, short, rounded, united 

 in the upper portion of the frond for some distance above 

 their attachments, separate in the lower portions ; mid- 

 nerve, slightly flexuous, and not strongly marked ; lateral 

 nerves, passing off at an acute angle, forking once near the 

 margin of the pinnule or lobe, and arching slightly up- 

 wards.) 



Some forms of this plant have a slight resemblace to P. 

 concinna., Lesqx. in the mode of nervation, but in our 

 plant the lateral nerves fork, while in P. concinna they are 

 mostly simple. 



Habitat. — Roof-shales of the Waynesburg Coal, Cass- 

 ville, W. Va. 



Pecopteris platynerms, Sp. nov., PL XVIII, Figs. 1-6. 



(Frond, tripinnate ; primary rachis, strong, rough, and 

 marked with pointed dot-like elevations ; secondary pinnae, 

 alternate, linear-lanceolate, going off at nearly a right 

 angle ; secondary rachis, stout at the insertion, but taper- 

 ing rather rapidly to the apex, where it is rather sleuder ; 

 pinnules, short, oblong, obtusely rounded at the apex, sep- 

 arate to the base in the lower and nuddle portions of the 

 frond, becoming more and more united toward the summit, 

 until they pass through pinnules with lobed and undulate 

 borders finally into simple pinnules of the normal form ; 

 mid-nerve of the pinnules well marked and distinct to the 

 apex ; lateral nerves broad and flat, usually forking just at 

 the point of insertion, thence diverging, without bninching 

 and almost without arching, to the margin, thus forming a 



