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SPENCER : THE HALIFAX COAL STRATA. 
Afterwards the whole area rose above the water, and a land 
surface was formed which probably endured for hundreds of years, 
and was covered by vast forests of Carboniferous trees and ferns, 
which ultimately became converted into the Hard Bed coal. The 
magnificent flora of this epoch, fortunately for science, has been well 
preserved in our coal-balls, which occur in this seam. The fossil 
plants found in these coal-balls, have their internal structure perfectly 
preserved. The balls contain fragments of lepidodendron in great 
abundance and variety, sigillaria, stigmaria, calamites, cycads, tree 
ferns and other ferns in great numbers ; also spores, fruits, nuts, 
seeds, etc., all shewing their internal structure under the microscope. 
Perhaps one of the most interesting discoveries made in connection 
with these coal-balls, was the finding of fossil fungi in the interior 
of many of the fossil plants, and in a splendid state of preservation. 
Marine Strata Overlying the Hard Bed Coals. 
After the growth of the vegetation w^hich produced this coal, 
the physiography of the whole area changed from a land surface 
with a magnificent flora to a deep sea, but no great disturbance 
of the strata took place, for immediately overlying the coal is a bed 
of marine shells (Aviculopecten) of from 3 in. to 6 in. in thickness, 
which appears to be co-extensive with the coal. There are several 
species of Aviculopecten and also a few other shells, but the great 
majority belong to the species Aviculopecten ixipyraceous. Overlying 
the pecten bed there are from 3 ft. to 9 ft. of shales, containing 
a large number of roundish concretions locally called " Baum Pots," 
which are composed of black limestone and coated with iron pyrites. 
They are interesting to the geologist on account of their containing 
Goniatites listeri in great profusion and of all sizes, from of an 
inch or less to 2 in. or 3 in. in diameter, together with a large 
number of other fossil shells and fish-remains. Large specimens of 
G. listeri, Orthoceras, Nautili, <fec., and also occur in the shales free, 
i.e., not enclosed in nodules. 
The following list comprises most of the species found in these 
marine strata in the neighbourliood of Halifax : — 
