66 MR. J. W. KTRKBY ON PERMIAN FISH AND PLANTS. 



the limestone ; and it was in working these lower and inferior 

 strata that the great bulk of the fossil fish were discovered, most 

 of them having been found in one bed, or zone of beds, of lime- 

 stone ; there, nevertheless, being several instances of their occur- 

 rence both above and below that horizon. 



Soon after their discovery in the new quarry, another or the 

 same anticlinal brought up the equivalent strata in the old quarry, 

 about half a furlong to the south ; and it was not long before the 

 same fossils were met with there, besides other species that the 

 first locality had not yielded. 



The same fish-bed would appear also to extend considerably to 

 the north-east ; for I have obtained the tail-half of a small fish 

 from a stratum of limestone in Marsden Bay, occupying the same 

 stratigraphical position as the Fulwell Fish-bed.* 



The Magnesian Limestone worked in the Fulwell quarries 

 belongs to the higher portion of the Permian series, or, to speak 

 with precision, to the "Upper Limestone" of the classification 

 proposed by Mr. Howse, or to the Crystalline and Concretionary 

 Limestone of Professor King's arrangement. But it must be 

 further observed that the Upper Limestone of Durham is com- 

 posed of two portions, the higher being yellow, friable, or com- 

 pact, or oolitic, and thin-bedded, while the lower is of various 

 shades of yellow and grey, highly concretionary, compact, or 

 friable, and thick -bedded. It is the latter portion that is worked 

 in the quarries of Fulwell Hill, that district being situate beyond 

 the outcrop of the bigher strata. Tbe lower portion, which, for 

 the sake of convenience, I shall term the Fulwell beds, has been 

 further subdivided by the quarrymen into several minor groups. 

 These it will be well to mention, as they serve to mark with 

 greater exactness the vertical distribution of the fossils to be 

 described. 



Below the higher thin-bedded yellow limestone is a series of 

 thick beds of hard, subcrystalline, grey or whitish grey limestone, 



* It is possible tliat the fish-bed may extend to the south as -well as to the north of 

 Fulwell. Strata equivalent in position to it are occasionally exposed in excavating cel- 

 lars and foundations in Bridge Street, and thence a few hundred yards down High Street, 

 in Bishop wearmouth. They also occur in the form of a finely laminated, light yellow 

 limestone, between tide marks, opposite the Craggs, near Ryhope Half-way House. 



