Counties of Durham and Northumberland. 35 



helicina, Schloth. Numerous Entomostraca and Foraminifera. 

 Also the remains of Palaonisci, &c. 



Loc. Coast of Durham from Marsden Bay to Roker, between 

 Heudon and Ryhope, and between Seaham and Black Halls; 

 Cleadon Hills, Fulwell Hill, Building Hill, &c. 



Middle. 



3. Concretionary and Shell Limestone. — An amor- 

 phous irregular deposit of highly crystalline or saccharine lime- 

 stone, occasionally full of small, irregular cavities, partially or 

 entirely filled with a fine earthy yellowish powdery substance; 

 other parts present the appearance of being formed of shapeless 

 fragments of compact limestone imbedded in a completely in- 

 vesting matrix, without taking the form of a true breccia. Occa- 

 sionally, however, large angular masses of finely laminated lime- 

 stone are imbedded in it, especially towards its highest portion, 

 where it also gradually becomes more earthy, and in some locali- 

 ties regularly bedded. 



Its thickness is probably more than 150 feet. 



Without fossils. 



Loc. Tynemouth, North Point to Marsden Bay ; coast between 

 Ryhope, Seaham, and Castle Eden-dene ; banks of the Wear 

 above Sunderland Bridge ; Tunstall Hope. 



The Shell Limestone forming the westernmost or basseting 

 portion of the above deposit is an irregular mass of highly 

 crystalline limestone, in some parts exceedingly hard and fine- 

 grained, and in others friable, earthy and rubbly, consisting of 

 broken pieces of coral and shells. It contains an assemblage of 

 the most characteristic fossils of the system. When seen in 

 section it generally rests on the compact limestone, but at 

 Clack^s Heugh it rests also on a bed of incoherent sand. 



The thickness, owing perhaps to denudation, is not more than 

 50 feet. 



Char. Foss. — Terehratula elongata, Schloth. ; Camarophoria 

 Schlotheimi, v. Buch ; Spirifer undulatus, Sow. ; Strophalosia 

 Goldfussi, Miinst. ; Produdus horridus, Sow. ; Fenestella reti- 

 fo7'mis, Schloth. ; F. virgulacea, Phill., &c. &c. 



Loc. West Boldon, Hylton Castle, South wick Red House, 

 Clack^s Heugh, all on the escarpment. High Barns, Humbleton 

 Hill, Elstobs, Tunstall Hill, Ryhope Field House, Dalton-le-dale, 

 Castle Eden-dene. These places are situated on the middle por- 

 tions of the Magnesian liimestone. 



Lower. 



4. Compact Limestone and Conglomerate. — In most places 

 on the escarpment the compact limestone forms a very thick 



3* 



