living species. Probably many of
the ferns were epiphytic. _Pecopteris, Cyclopteris, Neuropteris,
Alethopteris, Sphenopteris_ are common genera; _Megaphyton_ and
_Caulopteris_ were tree ferns. Our modern diminutive "horse-tails"
with scaly leaves were represented in the Carboniferous period by
gigantic calamites, often with a diameter of 1 to 2 ft. and a height
of 50 to 90 ft. The Carboniferous forerunners of the tiny club-moss
were then great trees with dichotomously branching stems and crowded
linear leaves, such as _Lepidodendron_ (with its fruit cone called
_Lepidostrobus), Halonia, Lepidophloios_ and _Sigillaria_, the largest
plants of the period, with trunks sometimes 5 ft. in diameter and 100
ft. high. The roots of several of these forms are known as _Stigmaria.
Sphenophyllum_ was a slender climbing plant with whorls of leaves,
which was probably related both to the calamites and the lycopods.
_Cordaites_, a tall plant (20-30 ft.) with yucca-like leaves, was
related to the cycads and conifers; the catkin-like inflorescence,
which bore yew-like berries, is called _Cardiocarpus_. Many large
trees which have been looked upon as conifers on account of their wood
structure may perhaps belong more properly to the Cordaitales. True
coniferous trees (_Walchia_) do appear at the top of the coal
measures.

The animals preserved in the continental type of Carboniferous deposit
naturally differ markedly from the fossil remains of the purely marine
portions of the system. The inhabitants of the waters of this
geographical phase include mollusca, which are supposed to have lived
in brackish or fresh water, such as _Anthracomya, Naiadites,
Carbonicola_, and many forms of Crustacea, e.g. (_Bairdia Carbonia_),
phyllopods (_Estheria_), phyllocarids (_Acanthocaris, Dithyrocaris_),
schizopods (_Anthrapalaemon_), Eurypterids (_Eurypterus,
Glyptoscorpius_). Fishes were abundant, many of the smaller ganoids
are beautifully preserved in an entire condition, other larger forms
are represented by fin spines, teeth and bones; _Ctenodus, Uronemus,
Acanthodes, Cheirodus, Gyracanthus_ are characteristic genera.

Frequently a temporary return of marine conditions permitted the
entombment of such salt water genera as _Lingula, Orbiculoidea,
Productus_ in the thin beds known as "marine bands."

Remains of air-breathing insects, myriapods and arachnids show that
these fo