ms Brgt., some 
which they are overlaid, or sometimes replaced. Thus, in the 
absence of other remains, or until I had discovered them, the 
abundance of Stigmaria ficoides in the roof-shales has helped me 
to identify this coal in many places. 
The roof shales of No. 1B coal are occasionally overlaid by 
a stratum of limestone or argillaceous shale, containing a great 
abundance of fossil shells. Locally also, and where this lime- 
Stone is absent, its place is taken by a bed of coal, variable in 
thickness from one to four feet. -Asit is rarely formed, and some- 
times in close proximity to No. 1B, I consider it still as a mem- 
ber of No. 1B; and it is accordingly ranked in my sections as No. 
Coal No. 2, is generally placed at about one hundred feet above 
No. 1B, and separated from it by various strata of shales and 
Sandstone, and occasionally by the limestone mentioned before, 
or also by a cherty compound named Burrstone. Its roof-shales 
* It is particularly well developed in the northern part of the coal basin of Illi- 
Rois and Indiana where I have seen it lately from four to six feet thick of pretty 
800d coal, 
a 
ars 
