176 GEOLOGY OF OHIO. 
shall, therefore, confine myself in this chapter toa few words in reference 
to the strictly geological bearing of the fossils contained in the Coal 
Measures, 
The question is often asked how far the plant impressions that are 
found associated in such abundance with the coal strata are characteris- 
tic of the different seams; and hence, how far can they be used as means 
for their identification. This is a subject which has engaged my atten- 
tion through many years, during which I have collected fossil plants 
from most of our Coal Measure area and strata. The result of my ob- 
servations is the conviction that co.» ratively little use can be made of 
fossil plants in the classification of coal seams. Many species run 
entirely through the series, and most are common to two or more coals. 
With the exception of Coal No. 1, which has a very abundant flora, and 
one that contains many plants not yet found elsewhere, I know of no one 
of our coal strata that can be certainly identified by its fossil plants. In 
a general way, our Carboniferous flora may be divided into three stages, 
as follows: 
1st. The Lower Carboniferous flora, represented chiefly by the remark- 
able group of fossil plants collected by Prof. Andrews, and described in 
the Paleontological portion of this Report. This flora has the greatest 
affinity with the Sub-Carboniferous and Devonian floras of West Vir- 
ginia described by Prof. Fontaine, and of New York, Maine and Canada, 
so fully illustrated in the admirable reports of Prof. J. W. Dawson. | 
2d. The flora of the Conglomerate and Coal No. 1. This comprises 
probably one-half of all the species of fossil plants found in Ohio. In 
the Conglomerate the more delicate plants are rarely preserved, as in the 
coarse sandstones they have been destroyed by the trituration to which 
they were subjected. Trunks of Lepidodendron, Sigillaria, Calamites, and | 
nuts (Trigonocarpon) are, therefore, what we generally find in this forma- 
tion. In some localities, however, beds of shale, intercalated with the 
upper layers of the Conglomerate, have yielded me several species of 
ferns, all of which are identical with those found over Coal No.1. The 
flora of the lower coal is, as has been said, exceedingly rich. No careful 
enumeration of its species has been made, but they amount to not less 
than one hundred and fifty. This is the special home of the giant lyco- 
pods—Lepidodendron, Lepidophlotos, and Sigillarta. ‘The number of species 
of these genera has been greatly multiplied by describing under distinct 
names different portions of the plant—as root, stem, branches, leaves, 
and fruit—and also their stages of growth and varietal phases; but we 
may safely say that three-fourths of all the species of these genera found 
in Ohio are peculiar to the lower coal. The same is true of the Calamuites 
