X PERMIAN POSSILS. 



varied suite of fossils than was known to occur in the contemporaneous rocks of England, 

 or Germany, — their having no proper distinctive general title, except such as were 

 obviously inappropriate, — and in consideration of the general reception and fitness of 

 geographical names for co-ordinate groups, as exemplified by those previously in use, 

 — Sir R. Murchison was induced to apply to these deposits the term Permian, which, 

 it will be perceived, is derived from the name of the country in which they are most 

 extensively developed. 



The Permian system, as developed in the North of England, is divisible into six 

 distinct members, having the following order of superposition. 



a. Crystalline, earthy, compact, and oolitic limestones. 



b. Brecciated, and pseudo-brecciated limestones. 



c. Fossiliferous limestone. 



d. Compact limestone. 

 €. Marl-slate. 



/. Various coloured sandstones. 



By traversing certain districts in the County of Durham, the above order of 

 position will be observed Thus, passing from the edge of the limestone near 

 Bolden direct to the coast, we meet with, at the base of the CliflF on the west 

 side of Down Hill, a bed of freestone, — the lowest member of the series (/) ; next 

 the overlying Marl-slate {e), on which repose several beds of brown-coloured lime- 

 stone {d), the lowest of which are flaggy, and the highest gritty and imperfectly 

 concretionary. Following the direction of the dip of these deposits, that is. towards 

 the coast, we first meet with beds of light-coloured limestone (c), containing numerous 

 organic remains, as at Hylton-North-Farm, and Southwick-Lane-House : this is 

 succeeded in the ascending order, as in the West Cluarry at Southwick, by a variety 

 of beds generally of a brecciated and pseudo-brecciated character {b) ; and these in 

 their turn become overlaid by vast beds of crystalline and other limestones {a), 

 extensively worked in the Fulwell Quarries, and continued down to Roker Cliff's on 

 the coast, where they are lost in the German Ocean. It often happens that this order 

 of superposition is obscured by some of the beds becoming modified in character, or 

 some of the members being absent. The inferior limestone {d) is, in some places, 

 compact, and of a uniform dark gray colour (Midderidge) ; in other places it is deep 

 brown, imperfectly concretionary, thin bedded, and sometimes cellular (Harton, &c.) ; 

 and in a few others mottled, and ribboned with various shades of brown and gray 

 (Pallion) : it also varies in chemical composition, consisting in general simply of 

 carbonate of lime, to which is added, in a few localities, (Ferry-Hill, Johnston,) a 

 considerable portion of carbonate of magnesia. The highest member of the series 

 {a) is another deposit, varying even more decidedly in its characters : a bed at one place 

 may be crystalline, compact, and ash-coloured ; and at a few yards distance, earthy. 



