The _Protozoans_ of the Permian rocks are few in number, and
for the most part imperfectly known. A few _Foraminifera_ have
been obtained from the Magnesian Limestone of England, and the
same formation has yielded some ill-understood Sponges. It does
not seem, however, altogether impossible that some of the singular
"concretions" of this formation may ultimately prove to have an
organic structure, though others would appear to be clearly of
purely inorganic origin. From the Permian of Saxony, Professor
Geinitz has described two species of _Spongillopsis_, which he
believes to be most nearly allied to the existing fresh-water
Sponges (_Spongilla_). This observation has an interest as bearing
upon the mode of deposition and origin of the Permian sediments.
The _Coelenterates_ are represented in the Permian by but a few
Corals. These belong partly to the _Tabulate_ and partly to the
_Rugose_ division; but the latter great group, so abundantly
represented in Silurian, Devonian, and Carboniferous seas, is
now extraordinarily reduced in numbers, the British strata of
this age yielding only species of the single genus _Polycoelia_.
So far, therefore, as at present known, all the characteristic
genera of the Rugose Corals of the Carboniferous had become extinct
before the deposition of the limestones of the Middle Permian.
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