•FOSSIL PLANTS. 
501 
\ 
ject have been published at different times, with the modifications induced by 
the progress of the researches, a summary of what is positively ascertained as 
yet on the stratigraphical distribution of the vegetation of the Coal Measures 
is not out of place in this Report. (1) 
When researches are restricted to a limited area, or to basins of small extent, 
marked differences are recognizable in the species of vegetable remains in the 
shales, as well as in the essential vegetable components of each bed of coal. It 
is, then, an easy task to ascertain the relative position of the coal strata from 
the comparison of these remains. But when researches are extended over a 
wider area, changes of vegetation, evidently caused by geographical distribu¬ 
tion, become more and more appreciable, some of the predominant species of a 
recognized horizon disappearing at some localities, and giving place to others 
of different characters. A glance at our table of distribution puts this in full 
evidence. The coal beds of Morris, Colchester and Murphysborough, the two 
first on the northeastern and northwestern, the last on the southwestern bor¬ 
ders of the coal field of Illinois, are recognized, from all evidence, as repre¬ 
senting coal No. 2, of the Illinois section, (in vol. 3, p. 6, of this Report) the 
equivalent of coal 1 B, of the Kentucky Report. (2) 
Though the general character of the flora may be considered as the same, 
we find, by comparison of the species at Murphysborough, eight peculiar spe¬ 
cies ; •ll'Vt’Vmi'y in common with Colchester and Morris, and twelve in common 
with Morris only, or altogether, eight species proper, and seventeen in common 
with strata of the same horizon examined elsewhere in Illinois. Colchester 
and Morris have been more carefully searched for specimens and are nearer to 
each other. They have seventeen species in common, while Colchester has 
nine species not yet found at Morris, and Morris has forty-four' species, with¬ 
out counting those of Mazon creek, which, as yet, have not been seen at Col¬ 
chester. The coal of Duquoin, considered as No. 5, of the Illinois section, and 
the only one from which as yet we have in Illinois and from a higher hori¬ 
zon a number of fossil plants which can be used for comparison, has eleven 
species proper, and seventeen in common with some or all of the other named 
localities. Points of difference and identity are therefore as well marked for 
this bed of coal as if it belonged to the sa’rne horizon as the others, and the 
same differences are observable in the distribution of common or more pre- 
- tfdTfii'fiant species. For example, Neuropteris flcxuosa is most abundant at 
Murphysborough, and has not as yet been found at Colchester and Morris, 
where Pecopteris villosa and Callipteris Sullivantii are the predominant species; 
and these are but rarely found, or not at all, at Murphysborough. On the 
(1) See, on this subject especially, Penna. Geol. Rept., p. 837; Amer. Jour, of Sci. and 
Art, Nov. 1860. 
(2) All these strata are here marked according to the Illinois section. 
