MANUAL OF NATURAL HISTORY. 557 



Cardiocarpa, and Stigmaria with tubercles on the 

 stem, arranged in a spiral manner ; the Asterophyl- 

 lites, with its star-like whorls, the leaves of Flabel- 

 laria and Zeugophyllum, the fruits of Trigonocar- 

 pum and Musocarpum, and about forty species of 

 curious furrowed Sigillarice, most probably the 

 stems of extinct Coniferous plants. 



IV. PERMIAN, OR MAGNESIAN-LIMESTONE 

 GROUP. 



This formation is composed of fragments of moun- 

 tain-limestone, coal, shale, &c., cemented together 

 by a base of dolomite, or magnesian-limestone. The 

 organic remains of this group exhibit some resem- 

 blance to those of the Trias, or New Red-Sandstone, 

 but approach more closely to those of the Carboni- 

 ferous. 



The Permian system is developed fully in Russia, 

 and derives its name from Perm in that country ; 

 in the south-west of England the beds are composed 

 of dolomite ; in the north-east, of a yellow inag- 

 nesian-limestone, passing into slate, marl, and marl 

 with gypsum. The magnesian-limestone is employed 

 for architectural purposes, and was chosen as the 

 best stone for building the New Palace at West- 

 minster. 



The organic remains at present discovered, com- 

 prise seven species of Nothosaurus, a reptile of the 

 family of Ichthyosauridce, and Protosaurus an ex- 

 tinct genus of Lacertidce, from the Permian stage of 



