346 FOSSIL PLANTS. 
show distinctly the pedicels of the sporanges and the blades in 
their natural position, but even sporanges with their seeds have 
been found in them, without perceptible alteration. In the cross — 
section of these Lepidostrobi the sporange cells form a central 
row, which is surrounded by the blades in the form of a star. E- 
Peculiar species of plants and animals, or their fragments, seem 
to have been selected as the nuclei of these nodules. They con- 
tain, for example, an abundance of leaflets of various species of 
Neuropteris, especially N. hirsuta, of Alethopteris Serlii, of Pe- 
- copteris villosa, P. abbreviata, Hymenophyllites Clarkii, Annularia — 
longifolia, Stigmarioides, ete., which are either rare or have not yet 
been found in the shale at Morris, while these shales are rich in ; 
the remains of Odontopteris Schlotheimii, Alethopteris erosa, Ulo- a 
dendron, Carpolithes multistriatus, scarcely or not at all preserved 4 
in concretions. As the bank of shale bordering the bed of Mazon — 
creek has not yet been opened, these differences may result from 
geographical distribution. Yet, as the animals and plants of soft a 
texture, like the species of the genus Sigillarioides, have not yet 
been found in the shale of our American Coal Measures, it is evi- 
dent that these remains have been generally destroyed by macera 
tion, and only escaped total destruction by their entombment in 
these nodules. The same can be remarked on the remains of 
small animals. The remains of fishes found in these concretions 
are merely bones, scales and coprolites; while of molluscs, they 
have afforded only some agglomerations or very small shells. 
VEGETABLE Remains PRESERVED BY MINERALIZATION OR TRUE 
Perrirication.— This kind of fossilization is performed by slow 
infiltration of mineral matter into the substance of the vegetable, — 
when in a soft state of decomposition. The phenomenon is pro- 
duced either by a total destruction of the vegetable substance, 10r 
which sand, clay or oxyd of iron is substituted by infiltration, OT 
by a slow, still unexplained mineralization of the vegetable sub- 
stance, by silex or lime. By the first process, the whole texture 
of the vegetable is destroyed, except the surface, preserved as in 
a mould, which shows the original outline of the vegetable, and 
bears the cicatrices of the bark and other external : 
which often render it recognizable. These moulds, generally ¢ 
ered by a coat of coaly matter, are rarely flattened by compres 
sion, and mostly represent trunks or branches of large size, Some 
= 
deal 
