FOSSILS OF THE PERMIAN. 67 



formation is the Magnesian Limestone ; it occurs 

 in certain portions of our sea-shores, as for example 

 from Tynemouth to Hartlepool, at St. Bees Head, 

 and at Maryport. It is the last, and least ancient of 

 the Palaeozoic formations, and is characterised by 

 a peculiar type of organic remains, and by an entire 

 absence of any species of fossil that occurs in the 

 newer strata. Between the period of the Permian 

 formation and the most ancient of the secondary 

 strata, one of the two grand revolutions in the 

 organic world occurred, and hence the fossil re- 

 mains of the Permian possess great interest, as 

 exhibiting the last and most advanced condition 

 of organic life in the Palaeozoic era, and as being 

 separated by a vast and marvellous revolution from 

 the succeeding epoch. 



The plants of this formation are such as are 

 common to the coal measures, and the same remark 

 may be made as to a large number of the Kadiata, 

 Mollusca, and Articulata. Of the trilobites which 

 swarmed in the Silurian seas, and which occurred 

 to a limited extent in the Carboniferous formation, 

 there are no traces whatever in the Permian. 



The fishes of the Permian comprise about fifty 

 species. They all seem to have possessed the pecu- 

 liar modification of the tail in which the vertebral 

 column is prolonged into the upper lobe of the 

 caudal fins. This remarkable structure of the 

 caudal fin, although apparently universal among 

 the fishes of the Permian group, is found to be 

 of excessive rarity in the fishes of the secondary 



and tertiary epochs ; and at the present day almost 



F 2 



