FOSSIL PLANTS. 419 



and numerous, uniform, at right angles to the middle nerve, decurring 

 to it at the point of attachment, forking once very near the base. The 

 rectangular character of the nervation has suggested the name of the 

 genus. 



This genus is allied to Tseniopteris, Brongt., Angiopteridium, Sch., and 

 Neriopteris, Newb. The nervation is similar to Tcvniopteris, but Tseniop- 

 teris has a simple frond, while this is pinnate. In Angiopteridium the 

 frond is pinnate, and the pinnae have cordate or rounded bases and acute- 

 angled nervation, with a marginal and bivalvular fructification; and 

 in Neriopteris the pinna? are similarly cordate or rounded, with acute- 

 angled nervation, and with a supposed marginal fructification. In this 

 genus the pinnse, on the other hand, are decurrent below, rounded and 

 free above, with rectangular nervation. It has more of the characters 

 of the Danpca than any of the Pecopterideas of the Coal Measures, the 

 veins being parallel, equal, and slightly turning up at or near the mar- 

 gin. It differs, however, by the decurrent base of the leaflets, in which 

 feature it is allied to the Alethopteris. It doubtless belongs to the order 

 of the Txniopteridese. None of this order have hitherto been found so 

 low as in the Coal Measures. T. multinervis, Weiss, belongs to the Upper 

 Coal Measures and Permian of Europe. The only plants of this order 

 found in this country, so far as I know, are Tseniopteris {Macrotxniopteris, 

 Sch.) magnijolia, Rogers, in the Triassic coal field near Richmond, Vir- 

 ginia, and T. vittata, reported by Dr. Hitchcock, from the Triassic of the 

 Connecticut valley. In Ohio plants of this type are singularly found 

 associated with several Devonian types, such as MegalopteriSy Daw., and 

 ArchxojAeris (^Palseopteris), Daw. 



OkTHOGONIOPTERIS CLARA (sp. IIOV.). 

 Plate 50, figs. 1 and la. 

 Frond pinnate. Stalk of medium size, with numerous closely set pin- 

 nae. Pinna? alternate, oblong-linear, rounded, and tapering to an acute 

 point. Entire or slightly undulate, diverging from the rachis at a not 

 very acute angle; margins contiguous or over-lapping; the upper mar- 

 gin rounded at the base, meeting the medial nerve a short distance from 

 its junction with the rachis ; the lower margin decurrent, the alate por- 

 tion extending down the rachis nearly to the medial nerve of the 

 next pinna. Medial nerve very prominent, extending to apex of 

 pinna. Nervules very fine and close, leaving the medial nerve at a 

 very acute angle, forking once very near their bases, then, bending 

 sharply down to a horizontal line, extend parallel nearly to the mar- 



