420 
ELEMENTS OF GEOLOGY. 
CHAPTER XXIV. 
PLOKA AND FAUNA OF THE CARBONIFEROUS PERIOD. 
Vegetation of the Coal Period.—Ferns, Lycopodiacete, Equisetacese, Sigilla- 
rise, Stigmarise, Coniferse.—Angiosperms;—Climate of the Coal Period.-^ 
Mountain Limestone.—Marine Fauna of the Carboniferous Period.—Corals. 
—Bryozoa, Crinoidea.—Mollusca.—Great Number of fossil Fish.—Fora- 
minifera. 
Vegetation of the Coal Period. — In the last chapter we 
have seen that the seams of coal, whether bituminous or an¬ 
thracitic, are derived from the same species of plants, and 
Goppert has ascertained that the remains of every family of 
plants scattered through the shales* and sandstones of the 
coal-measures are sometimes met with in the pure coal itself 
—a fact which adds greatly to the geological interest of this 
flora. 
The coal period was called by Adolphe Brongniart the age 
of Acrogens,"^ so great appears to have been the numerical 
preponderance of flowerless or cryptogamic plants of the 
families of ferns, club-mosses, and horse-tails. He reckoned 
the known species in 1849 at 500, and the number has been 
largely increased by recent research in spite of reductions 
owing to the discovery that different parts of even the same 
plants had been taken for distinct species. Notwithstanding 
these changes, Brongniart’s generalization concerning this 
flora still holds true, namely, that the state of the vegetable 
world was then extremely diflereiit from that now prevailing, 
not only because the cryptogamous plants constituted nearly 
the whole flora, but also because they were, on the whole, 
more highly developed than any belonging to the same class 
now existing, and united some forms of structure now only 
found separately and in distinct orders. The only phaenoga- 
mous plants which constitute any feature in the coal are the 
coniferae; monocotyledonous angiosperms appear to have 
been very rare, and the dicotyledonous, with one or two 
doubtful exceptions, were wanting. For this we are in some 
measure prepared by what we have seen of the Secondary or 
Mesozoic floras if, consistently with the belief in the theory 
of evolution, we expect to find the prevalence of simpler and 
less specialized organisms in older rocks. 
* For botanical nomenclature, see p. 304. 
