THE PERMIAN PERIOD. 201 



and belong in part to Carboniferous genera. A characteristic 

 genus, however, is Walchia (fig. 134), distinguished by its lax 

 short leaves. This genus, though not exclusively Permian, is 

 mainly so, the best-known species being the W. piniformis. 

 Here, also, we meet with Conifers which produce true cones, 

 and which differ, therefore, in an important degree from the 

 Taxoid Conifers of the Coal-measures. Besides Walchia, a 

 characteristic form of these is the Ullmania selaginoides, which 

 occurs in the Magnesian Limestone of Durham, the Middle 

 Permian of Westmorland, and the " Kupfer-schiefer " of Ger- 

 many. The group of the Cycads, which we shall subsequently 

 find to be so characteristic of the vegetation of the Secondary 

 period, is, on the other hand, only doubtfully represented in 

 the Permian deposits by the singular genus Nceggerathia. 



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 de- 

 position and origin of the Permian sediments. 



The Ccelenterates 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 abun- 

 dantly 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 

 Polyccclia. 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 Echinodcrms are represented by a few Crinoids, and by a 

 Sea-urchin belonging to the genus Eocidaris. The latter genus 

 is nearly allied to the Archceocidaris of the Carboniferous, so 

 that this Permian form belongs to a characteristically Palaeozoic 

 type. 



A few Annelides (Spirorbis, Vermilia, &c.) have been de- 



