MUSEUM OF THE NATURAL HISTORY SOCIETY. 231 



The discovery of the upper memhers of this group of strata 

 in the South Durham, enahles one to correlate it more exactly 

 with the same heels in Yorkshire arid in Germany, especially with 

 the latter, where it has for a long time heen known to contain 

 deposits of Rock-Salt. The following divisions of the llagnesian- 

 limestone were proposed by myself in 1857, and have heen 

 adopted by Mr. James Kirkby, Dr. Geinitz, Dr. Davison, Robt. 

 Etheridge, and others. — See Ann. Nat. Hist., 1857, and Trans. 

 Tyneside Nat. P. Club, Vol. 3, p. 235, 1858. 



Upper Series of Magnesian-Umestone Beds. 

 1 . Beothebton beds of Yorkshire = Plattendolomit of Germany. 



These beds have only recently been discovered in the borings 

 for salt in the South of Durham, and known only by the section 

 shewn in the cores. There is no difficulty in identifying this 

 thin upper limestone with the Brotherton and Knottiugley beds 

 of Yorkshire and the Plattendolomit of Germany. 



Fossils. — The characteristic fossils of this bed in Yorkshire 

 and Germany are — 



Myalina Hausmanni, Goldf., Perm. Poss., PI. 14, f. 1-14. 

 Axinus dubius, (Schloth.) Perm. Poss., PI. 15, f. 23-32. 

 Chondrites virgatus, Miinst., Dyas, PL 24, f. 5; PL 28, f. 6. 



I cannot say with certainty that any fossils have been found 

 or have been searched for in the cores of this uppermost lime- 

 stone in South Durham, but in the boring on the side of Tees, 

 put down by the Newcastle Chemical Company, the three 

 species above enumerated have been found by myself and Dr. 

 Yeitch. The cores of this boring had been so much disordered 

 that the exact position of the fossils could not be satisfactorily 

 determined. That they were in the higher beds of limestone 

 there could be no doubt, as beds of oolitic structure, identical with 

 some beds near Hartlepool, were arranged with the fossiliferous 

 cores. The very diminished and dwarfed size of the shells proves 

 that they existed, in the bed of the then Permian sea, under 

 conditions inimical to Holluscan life, and were fast being de- 

 prived of the power of existence. 



