Counties of Durham and Northumberland. 37 



deposit of thiu-bedded, compact, bluish, grey or mottled lime- 

 stone, becoming occasionally brown, earthy, cellular, and with 

 thicker beds towards the top. 



It attains a thickness probably of 150 to 200 feet. 



Char. Foss. — Same as in shell-limestone, but not so abun- 

 dant. 



Loc. WTiitley, Cullercoats, Tyncmouth, outliers ; from North 

 Point to Man Haven, surmounted by concretionary limestone ; 

 Westoe, West Boldon, Hylton Castle, Clack's Heugh, Pallion, 

 Mill Field, Humbleton, Tunstall Hope, Painshaw Hill, and most 

 other parts of the escarpment to Pierce Bridge. 



The Conglomerate is a very local deposit of rounded fragments 

 of compact limestone imbedded in a limestone matrix. It is of 

 inconsiderable thickness, and passes into the associated compact 

 limestone. 



CuAR. Foss. — Same as in compact limestone. 



Loc. Tynemouthj Black Halls ? Houghton-le-side ? 



3. Marl Slate. 



The Marl-slate is a very thin deposit, seldom exceeding a 

 yard in thickness, of a dark grey, or yellowish, finely laminated 

 marl. 



Char. Foss. — Palaonisci, Platysomi, and other fishes; Dis- 

 cina Konincki, Gein. ; Lingula Credneri, Gein. ; Caulerpites 

 selaginoides, Schloth., and other fucoids. 



Loc. Cullercoats, Tynemouth, Westoe, West Boldon, Clack^s 

 Heugh, and most other places on the escarpment. 



General Bemarks. 



The foregoing divisions include all the beds which can be with 

 safety referred to, and satisfactorily determined to belong to the 

 Permian System as developed in the counties of Durham 

 and Northumberland. But it has hitherto been the custom of 

 English geologists to consider an extensive bed of incoherent 

 yellow sand and red sandstone lying immediately beneath these, 

 as members of the same system, and to separate them by a di- 

 stinctive name from the subjacent coal-measures, with which they 

 are perfectly conformable, and, so far as the red sandstone is 

 concerned, identical in fossil contents. At Cullercoats and 

 Tynemouth the red sandstone is so evidently conformable, and 

 passes so gradually into the shales and sandstones of the true 

 coal-measures, that it is impossible to separate them, or point 

 out a line of separation. The same arrangement also is seen on 

 the banks of the Wear, near Clack's Heugh, where both these beds 

 are seen dipping at the same angle as the coal-measures. 



