920 CATALOGUE OF THE FOSSILS OF THE PERMIAN SYSTEM 
members in the ascending order are—the Lower-new-red-sand- 
stone, Marl-slate, Magnesian-limestone, and Upper-new-red- 
sandstone. These rocks occupy the whole of the eastern part of 
the county of Durham, from a line drawn through the following 
places, wiz. :—Westoe, Harton, Cleadon, West Boldon, Hylton 
Castle, Pallion, Clack’s Heugh, Painshaw, West Herrington, 
Houghton-le-Spring, Moorsley, Pittington, Sherburn, Quarring- 
ton, Coxhoe, Cornforth, Thrislington, Ferry hill, Merrington, 
Westerton, Coundon Grange, Eldon, East Thickley, Midderidge 
Grange, West Thickley, Newbiggen, Shackerton Hill, White- 
house, Houghton-le-Side, Langton, Ingleton, Morton-Tinmouth, 
and Pierce Bridge, where it crosses the Tees. The greatest 
width of the Magnesian-limestone is about fourteen miles, be- 
tween Cornforth on the west and Hartlepool on the coast. In 
the south-eastern part of the county, the whole of the surface is so 
much covered with alluvium that the nature of the subjacent 
rock cannot be easily ascertained. Three remarkable outliers 
belonging to this system are situated in Northumberland. The 
largest of these is near Whitley, the second is near Culler- 
coats, and the third forms the cap of the cliff on which Tyne- 
mouth Priory is situated. At a former period these outliers 
must have been connected with each other, and with the general 
mass of Magnesian-limestone which is seen on the coast at the 
south end of Shields sands. 
As the Lower-new-red-sandstone and Marl-slate are generally 
seen only in the escarpment they do not occasion any material 
change in the outward appearance of the country, but the ex- 
ternal features of the Magnesian-limestone are well mark- 
ed, and peculiar. The escarpment on the west is rather 
abrupt, and forms an undulating line of more or less ele- 
vated eminences. In the interior the surface is broken by nu- 
merous, low, rounded hills, which are separated from each other 
by shortened vallies or “hopes.” Towards the coast, extensive 
“denes” occur; which afford a passage for the small streams or 
burns which run from the escarpment towards the sea. Some 
of these denes are extremely picturesque and beautiful. In the 
first part of their course they are open and shallow, but as they 
