176 GEOLOGY OF OHIO. 



shall, therefore, confine myself in this chapter to a 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 c<">ii-j> iratively little use can be made of 

 fossil plants in the classification ox 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 PalaBontological 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, Catamites, 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, Lepidophloios, and Sigillaria. 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 Calamites 



