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.

The Echinoderms are represented by a few Crinoids, and by a Sea-urchin belonging to the genus Eocidaris.  The latter genus is nearly allied to the Archoeocidaris of the Carboniferous, so that this Permian form belongs to a characteristically Palaeozoic type.

A few Annelides (Spirorbis, Vermilia, &c.) have been described, but are of no special importance.  Amongst the Crustaceans, however, we have to note the total absence of the great Palaeozoic group of the Trilobites; whilst the little Ostracoda and Phyllopods still continue to be represented.  We have also to note the first appearance here of the “Short-tailed” Decapods or Crabs (Brachyura), the highest of all the groups of Crustacea, in the person of Hemitrochiscus paradoxus, an extremely minute Crab from the Permian of Germany.

[Illustration:  Fig. 135.—­Brachiopods of the Permian formation. a, Producta horrida; b, Lingula Credneri; c, Terebratula elongata; d and e, Camarophoria globulina. (After King.)]

Amongst the Mollusca, the remains of Polyzoa may fairly be said to be amongst the most abundant of all the fossils of the Permian formation, The principal forms of these are the fronds of the Lace-corals (Fenestella, Retepora, and Synocladia), which are very abundant in the Magnesian Limestone of the north of England, and belong to various highly characteristic species (such as Fenestella retiformis, Retepora Ehrenbergi, and Synocladia virgulacea).