many subsidences to be followed by an equal number of pauses, 
which enabled fresh vegetation to grow, but only to be again 
submerged. Most Coalfields show by the Fauna that the Flora 
was submerged not always by salt or fresh water, but at one 
time it was fresh, at another salt, and again by a mixture of 
the two or estuarine. 
This indicates that the plants grew in close proximity both 
to the sea and fresh water at different times. Of submergence 
by fresh water we have evidence in fresh water Limestones, 
composed for the most part of Spirorbis carbonarius in some 
parts of England. 
In the Bristol Coalfield the indications of alternations of 
marine, fresh, and estuarine deposits are not indicated by any 
Fauna found up to the present time, though a diligent search 
has been made for Fossils. 
Tf now we turn to our section of the Bristol Coalfield, we at 
once get a general view of it (see section). First comes the 
Carboniferous Limestone, divided into the Lower Shales, Moun- 
tain Limestone, and Upper Shales. The Lower Shales rest 
conformably on Devonian strata, the break being a paleeonto- 
logical one determined by the Fauna, but the Flora of the 
Mountain Limestone is more Devonian than Carboniferous. 
According to Gorrrsrr,* the Mountain Limestone (Kohlenkalk) 
examined by him contained 47 species, of which 46 were terres- 
trial plants belonging to the same families as occur in the Upper 
Devonian. 
We might naturally suppose this to be the case, as we have 
abundant evidence that during the deposition of the Limestone 
a Devonian land surface existed. Thus the Coal measures in some 
parts of the centre of England are defective at their base, the 
Limestone being absent. There must then have been land where 
this defect occurs, on which we can see no reason why a Devonian 
Flora should not have flourished and been carried by rivers to 
the sea in which the Limestone was forming. 
* On the Flora of the Siberian Devonian and lower Carboniferous formations, 
Geo. Soc., Vol. 16, p. 279, 1860. 
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