onia, Euomphalus, Naticopsis_). The Pteropods were well
represented by _Conularia_ and _Bellerophon_. Amongst the Cephalopods,
the most striking feature is the rise and development of the
Goniatites (_Glyphioceras, Gastrioceras_, &c.); straight-shelled forms
still lived on in some variety (_Orthoceras, Actinoceras_), along with
numerous nautiloids.

Trilobites during this period sank to a very subordinate position, but
Ostracods (_Cythere, Kirkbya, Beyrichia_) were abundant.

Many fish inhabited the Carboniferous seas and most of these were
Elasmobranchs, sharks with crushing pavement teeth (_Psammodus_),
adapted for grinding the shells of brachiopods, crustaceans, &c. Other
sharks had piercing teeth (_Cladoselache_ and _Cladodus_); some, the
petalodonts, had peculiar cycloid cutting teeth. The Arthrodirans, so
prominent during the Devonian period, disappeared before the close of
the Carboniferous. Most of the sharks lived in the sea continuously,
but the ganoids frequenting the coastal waters appear to have migrated
inland. About 700 species of Carboniferous fish have been described
largely from teeth, spines and dermal ossicles.

(2) _Flora and Fauna of the Lagoonal or Continental Facies._--The
strata deposited during this period are the earliest in which the
remains of plants take a prominent place. The fossil plants which are
found in the upper beds of the preceding Devonian system are so
closely related to those in the Lower Carboniferous, that from a
palaeobotanical standpoint the two form one indivisible period.

In the Lower Carboniferous the flora was composed of six great groups
of plants, viz. the Equisetales (Horse-tails), the Lycopodiales (Club
mosses), the Filicales (Ferns) and Cycadofilices, the Sphenophyllales
and Cordaitales. These six groups were the dominant types throughout
the period, but during Upper Carboniferous time three other groups
arose, the Coniferales, the Cycadophyta, and the Ginkgoales (of which
_Ginkgo biloba_ is the only modern representative). Algae and fungi
also were present, but there were no flowering plants. The true ferns,
including tree ferns with a height of upwards of 60 ft., were
associated with many plants possessing a fern-like habit
(Cycadofilices) and others whose affinities have not yet been
definitely determined. The fronds of some of these Carboniferous ferns
are almost identical with those of