﻿1861.] 



KIEKBY PERMIAN", SOUTH YORKSHIRE. 



323 



tion. In referring these beds to the highest member of the Permian 

 series as developed in the North of England, Prof. King relies on 

 their lithological, chemical, and palaeontological characters, all of 

 which are stated to offer a remarkably close agreement with the 

 equivalent features of the highest Permian member of the North of 

 England*. Now, in the first place, the lithological evidence of the 

 Upper Limestone of the North of England is of very little value as an 

 aid to classification. In proof of this I would refer to the Brother- 

 ton Beds of Yorkshire, which are as different lithologically from the 

 Upper Limestone of Durham as they are from any other Permian 

 limestone whatever, though their relative position and fossil remains 

 indisputably prove them to be of the same general horizon. The 

 lithological characters of the Upper Limestone of Durham are peculiar 

 to that county ; and so are those of the Brotherton Beds to the ad- 

 joining counties of Yorkshire and Nottingham. Indeed to take the 

 Magnesian-limestone group as a whole, I question whether there, is 

 any series of rocks whose lithological characters are so variable and 

 of so little value in the classification of its different parts. And 

 so it is with the chemical composition of the Upper Limestone. Even 

 in Durham alone, analyses of its different beds show as great a varia- 

 tion in the proportion of chief ingredients as do analyses of limestones 

 of different members. Besides, analyses of the underlying members 

 sometimes so nearly agree with those of the upper, as to destroy the 

 worth of all arguments for the identity of age of different beds from 

 their similarity of chemical compositionf . And in respect to the fos- 

 sils, there certainly does not seem to be much reason for considering 

 them as a group characteristic of the upper beds. Out of the 11 

 species that occur, 6 (viz. Sten. Mackrothi, Th. dubius, Gerv. antiqua, 

 Tur. Altenburgensis, Ris. Leiglii, and Mil. pusilla) have never been 

 found higher than the middle subdivision or Shell-limestone of Dur- 

 ham. And, as Prof. King has justly pointed out, the absence of 

 Polyzoa among the species occurring in the upper member is one of 

 the peculiar characteristics of its faunaj. Eor this reason I must 

 conclude that the occurrence of two species of this class in the Tully- 

 connell deposit is opposed to its being considered the equivalent of 

 that member. Eour of the species — viz. Ax. dubius, Myal. Hausmanni, 



* Loc. cit. p. 79. 



f I would refer to the following analyses in corroboration of this assertion. 

 The first is one of the Upper Limestone with which Prof. King has identified 

 the Irish deposit ; the other is one of the Compact Limestone, the most inferior 

 limestone member. 



Upper Limestone, Hartlepool. Compact Limestone, Ferry Sill. 



Carbonate of Lime 545 Carbonate of Lime 54*1 



of Magnesia 44-9 of Magnesia 447 



Oxide of Iron 03 Oxide of Iron 0-6 



Earthy matter 03 Earthy matter 06 



100-0 100-0 

 Green well's Mine-engineering, p. 17. 

 + Mon. Perm. Eoss. of England, Introduction, pp. xiv, xvi ; and paper " On 

 the Occurrence of Permian Magnesian Limestone at Tullyconnell, near Artrea, in 

 the County of Tyrone," Journ, Geol. Soc. of Dublin, vol. vii. p. 60. 



