538 C.T. Trechmann—Brachiopods from Durham. 
Some Remarkably Preserved Brachiopods from the 
Lower Magnesian Limestone of Durham. 
By C. T. Trecumann, D.Sc., F.G.S. 
(PLATE XII.) 
Soe quarries in the neighbourhood of Shildon, near Bishop 
Auckland in South Durham, display interesting sections of the 
Lower Magnesian Limestones and the beds on which they rest. 
At present the most instructive is that at East Thickley, near Snildon 
railway station, and as there seems a probability in the near future 
of this quarry becoming obscured by pit refuse, a record of the section 
exposed in it seems to be desirable. A large part of the rock-face has 
already been so obscured. A short distance south-east of this one 
other quarries exist closely adjoiming the railway, but they are now 
almost entirely filled up with rubbish though sections in the railway 
cutting may still be seen. About a mile south-west of Thickley across 
the railway a quarry is at present being worked near Midderidge 
Grange, and seems to be the one in which important reptilian and 
other vertebrate remains were found in the Marl Slate many years 
ago. Notable among these is the headless skeleton of Proterosaurus 
Huxleyt Hancock & Howse,! each bone of which has the interior 
filled with galena. This and other important specimens are now 
in the Hancock Museum at Newcastle-on-Tvne. At present, how- 
ever, the only rock visible m Midderidge Quarry is the dolomitic 
Lower Magnesian Limestone, in which no fossils are to be seen. 
These quarries are either, as in the case of Hast Thickley, situated 
on the junction of the Permian with the Coal Measures, or, in the 
case of Midderidge, very close to the junction. 
Returning to Kast Thickley (Fig. 1), where about 45 feet of rock - 
is exposed in the quarry face, we find that the lowest bed consists 
of sandstones of the Coal Measures between the Harvey & Brockwell 
seams. ‘These are generally massive and curreut- bedded ; about 
12 feet of them are exposed and until a few years ago they were 
quarried as building stone. Above these come the Marl Slates, 
about 8 feet thick. At the base of the Marl Slate and resting on the 
Coal Measures there is an irregular hed a few inches thick of yellow 
dolomitie marl with sand and small rounded pebbles chiefly of 
quartz. It appears to fill up shallow depressions on the denuded 
surface of the Coal Measures and, may, perhaps, be regarded as the 
equivalent of the Yellow Sands of the Permian, which are absent in 
this section. This pebblvy bed is interesting as it contains numerous 
specimens of Lingula credner: Gein., the phosphatic shells of which 
are perfectly preserved even to the extent of retaining the different 
shades of colour on the bands of growth. Some of These Lingula 
valves are brown in colour, while others are bluish grey. 
The overlying Marl Slate still yields fish and plant remains, or did 
1 Q.J.G.S., vol. xxvi, 1870, p. 568. 
