PART II. CHAPTER XIX. 



241 



Fossils of the Magnesian Limestone. 



When we consider the fossils of the Magnesian Limestone in 

 England, or corresponding Zechstein in Germany, we find that 

 they approach much nearer in their character to the organic 

 remains of the older carboniferous group than to those of the 

 Upper New Red. Thus, for example, the two genera of shells, 

 Producta and Spirifer, of the family Brachiopoda, are common 



Fig. 240. 



Fig. 241. 



Magnesian Limestone. 



Spirifer undulatus, Sow. 

 Magnesian Limestone. 



to the Magnesian Limestone, Coal, and Primary fossiliferous 

 strata, but have never been met with in any rock above the 

 Magnesian Limestone. There are certain fish also found both 

 in England and Germany, in the Lower New Red System, 

 which occur in the carboniferous strata, but in no formation 

 higher in the series than the Magnesian limestone, not even in 

 the Muschelkalk. 



The genus Palaoniscus, Agas. (Pal&othrissum, Blain.) is 



Fig. 242. 



Restored outline of a fish of the genus Paleeoniscus. Agass.* Magnesian 

 Limestone. 



the most striking example, as three species have been found in 

 England in marl slate, immediately below the Magnesian Lime- 

 stone ; and three other different, but nearly allied species, in the 

 slate of the Zechstein of Germany, f 



It was first pointed out by M. Agassiz, that all the bony fish 

 of the Magnesian Limestone, and of all the more ancient form- 

 ations, have the vertebral column continued into the upper lobe 



* Poissons Fossiles, vol. i. tab. A. fig. 4. 



t Sedgwick, Geol. Trans., Second Series, vol. iii. p. 117. 



