CHAPTER VII. 
Description of the Fossils in the Mountain Limestone Formation of 
Yorkshire and of some other districts, arranged according to their 
Natural Affinities ; with Notices of the Strata in which each species 
occurs, and of the Localities where they are found. 
REMAINS OF PLANTS. 
r JL hese are distributed through the whole thickness of the system 
of carboniferous strata, which is above 6000 feet, but very unequally ; 
so that while 200 species are already described from the upper or 
coal measure formation, not ten have yet occurred to me in the mill- 
stone grit series, and still fewer in the sandstones and shales alternating 
with the mountain limestone. It does not appear that the species of 
plants are very characteristically different in these different stages of 
the carboniferous deposits; for the same stigmarne, lepidodendra, and 
sigillarise, are certainly found in all parts of the series. There is 
however to be noticed a greater prevalence of certain forms in strata 
occupying a given position, and a remarkable absence of other forms 
from particular parts of the section. Thus stigmaria ficoi'des, though 
it occurs in all parts of the series, is in a singular degree abundant 
in connexion with a few layers of fire clay and close grained grit- 
stone near the base of the coal measures. The numerous species of 
pecopteris, neuropteris, and other ferns, belong almost absolutely to 
the coal measures, (exceptions occur at Burdiehouses near Edinburgh 
and in north-west of Northumberland), stems of sternbergia abound 
in certain beds of millstone grit, and calamites, at least in Yorkshire, 
are most plentiful in and near the flagstone rock. In a very limited 
coal tract, some definite diagnostic characters of coal seams may be 
noticed, in accordance with Mr. Mammatt’s observations in the Ashby 
