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 Palæozoic 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 Palæozoic 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_). The _Brachiopoda_ are also represented in moderate numbers in the Permian. Along with species of the persistent genera _Discina, Crania_, and _Lingula_, we still meet with representatives of the old groups _Spirifera, Athyris_, and _Streptorhynchus_; and the Carboniferous _Productoe_ yet survive under well-marked and characteristic types, though in much-diminished numbers. The species of Brachiopods here figured (fig. 135) are characteristic of the Magnesian Limestone in Britain and of the corresponding strata on the Continent. Upon the whole, the most characteristic Permian _Brachiopods_ belong to the genera _Producta, Strophalosia_, and _Camarophoria_.