FOSSIL PLANTS. 393 



cies is generally rare, and its mode of fructification has not been observed be- 

 fore. 



It occurs in the concretions of Mazon creek. 



ALETHOPTERIS HYMENOPHYLLOIDES, Sp. nov. 



PI. x, fig. 1 to 4. 



FROND large, tripinnately divided, with primary and second- 

 ary pinnse alternate, turned upwards, ovate-lanceolate in out. 

 line, decurrent in a narrow-winged rachis ; secondary pinnae 

 or pinnules either entire, short oblong, obtusely pointed, joined 

 at the middle in acute sinuses; or longer, divided nearly to 

 the base, ovate-lanceolate and pinnately cut into regular ob- 

 tuse lobes with obtuse sinuses. In the short divisions, the 

 medial nerve only is distinguishable; in the larger ones, the 

 veins, though obscure, appear pinnately branching from the 

 medial nerve in an acute angle and forking at the middle. But 

 for this kind of nervation, this species should be considered as 

 a Hymenophyllites. 



Mazon creek ; in concretions of clay iron ore. 



ALETHOPTERIS INFLATA, Sp. nov. 



PI. x, fig. 5 and 6. 



NOTHING has been found of this species but the fragment 

 figured here. It shows part of a linear pinna, gradually taper- 

 ing to the point, divided into broadly ovate, or ovate obtusely 

 pointed lobes, enlarged and united near the base, marked in 

 the middle by a short thick nerve pinnately divided by five or 

 six pairs of arched veins forking once. The fructifications are 

 marked by oval inflated large fruit-dots, placed at the base of 

 the leaflets, one only on each side of the enlarged medial 

 nerve. The surface covering these inflated fruit-dots is 

 wrinkled above, and around them, as seen in fig. 6 enlarged. 

 50 



