FOSSIL PLANTS. 393 
cics is generally rare, and its mode of fructification has not been observed be¬ 
fore. 
It occurs in the concretions of Mazon creek. 
Aletiiopteris hymenophylloides, Sp. nov. 
592 c / 
PI. x, fig. 1 to 4. 
Sic- 
y O ' * J ////a r 
'•A/ /«* /o.i i/’-j / 
// 
Frond large, tripinnately divided, with primary and second¬ 
ary pinnae alternate, turned upwards, ovate-lanceolate in out¬ 
line, decurrent in a narrow-winged racliis; secondary pinnae 
or pinnules either entire, short oblong, obtusely pointed, joined 
at the n iddle in acute sinuses; or longer, divided nearly to 
the base, ovate-lanceolate and pinnately cut into regular ob- 
t ise 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 HymenophyHites. 
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 
