were armed with powerful conical
teeth, but the majority, like the existing Port Jackson shark, were
possessed of massive palates, suited in some cases for crushing, and in
others for cutting.

[Illustration: FIG. 24.--_Archegosaurus minor_. Coal-measures.]

[Illustration: FIG. 25.--_Psammodus porosus_. Crushing palate of a fish.]

[Illustration: FIG. 26.--_Orthoceras_. Mountain limestone.]

In the mountain limestone we see, of course, the predominance of marine
types, encrinital remains forming the greater proportion of the mass.
There are occasional plant remains which bear evidence of having drifted
for some distance from the shore. But next to the _encrinites_, the
corals are the most important and persistent. Corals of most beautiful
forms and capable of giving polished marble-like sections, are in
abundance. _Polyzoa_ are well represented, of which the lace-coral
(_fenestella_) and screw-coral (_archimedopora_) are instances.
_Cephalopoda_ are represented by the _orthoceras_, sometimes five or six
feet long, and _goniatites_, the forerunner of the familiar _ammonite_.
Many species of brachiopods and lammellibranchs are met with. _Lingula_,
most persistent throughout all geological time, is abundant in the
coal-shales, but not in the limestones. _Aviculopecten_ is there abundant
also. In the mountain limestone the last of the trilobites (_Phillipsia_)
is found.

[Illustration: FIG. 27.--_Fenestella retipora_. Mountain limestone.]

[Illustration: FIG. 28.--_Goniatites_. Mountain limestone.]

We have evidence of the existence in the forests of a variety of
_centipede_, specimens having been found in the erect stump of a hollow
tree, although the fossil is an extremely rare one. The same may be said
of the only two species of land-snail which have been found connected
with the coal forests, viz., _pupa vetusta_ and _zonites priscus_, both
discovered in the cliffs of Nova Scotia. These are sufficient to
demonstrate that the fauna of the period had already reached a high stage
of development. In the estuaries of the day, masses of a species of
freshwater mussel (_anthracosia_) were in existence, and these have left
their remains in the shape of extensive beds of shells. They are familiar
to the miner as _mussel-binds_, and are as noticeable a feature of this
long ago period, as are the aggregations of mussels on every coast at
the present day.

[Illustration: FIG. 29.--_Aviculopecten papyraceus_. Coal-shale.]