Carboniferous Period in East Scotland. 945 
Fells Oil-Shale separated from the Houston Coal above by about 300 feet of 
sandstone and shales. This coal seam was long ago extensively mined in 
West Lothian but is not at present considered worth exploiting. It is over- 
laid by the Houston Marls, a great thickness of clayey mudstones with 
calcareous and ferruginous bands. These marls, like those of Broxburn, are 
probably derived from the waste of basic volcanic rocks, and, indeed, the 
Houston Marls actually contain fragments of such rocks, as if they were in 
part volcanic tuffs. Above the marls comes the two-foot coal which is 
usually overlain almost immediately by a volcanic agglomerate. Two other 
oil-shale positions occur in the next few hundred feet—the lower is known as 
the Mungle Shale, that on the higher horizon is the Raeburn Shale position, 
in which there are two oil-shales, the upper being locally called the Fraser 
Shale, the highest worked oil-shale of the whole group which contains marine 
shells such as Lingula, orthoceratites and goniatites. Throughout the Oil-Shale 
field true clear-water marine organisms are rarely met with. At one horizon, 
however, the exact position of which is not accurately fixed, though it is 
below the Burdiehouse Limestone, a bed was discovered by Mr Macconochie, 
cropping out near Carlops, which has yielded a peculiar fauna of hinged 
brachiopods, Productws rhynchonellids, athyrids and hinged brachiopods 
and junciform Lithostrotion Bores, put down over the outcrop of the 
Burdiehouse or Raw Camps Limestone to the south of Harburn on the 
opposite side of the Pentlands from Carlops, tapped a band with encrinites 
and other marine forms which is probably on the same horizon. 
Besides the horizons just mentioned where marine or estuarine forms 
occur, there is another very interesting bed a little below the Pumpherston 
Shale position to which it acts as a sure index, as pointed out by Mr 
Carruthers.2 It contains goniatites, orthoceras and lamellibranchs, and a 
short distance beneath occurs a shrimp bed containing well-preserved 
erustacea of the genus Zealliocaris. Another marine bed occurs at Straiton 
in the Midlothian basin in the roof of one of the Dunnet Oil-Shales,*? which, 
in addition to containing orthoceratites, Zingul/a, and lamellibranchs, has 
yielded a large suite of fish remains, determined by Dr Traquair, and from 
which he considered that these fishes, and even those found in the Burdiehouse 
Limestone, were of estuarine habit. 
With regard to the Burdiehouse Limestone being of freshwater origin, 
1See remarks by Dr Lee in the Appendix to “Geology of the Neighbourhood of 
Edinburgh,” Mem. Geol. Sur., Second Edition, 1910, p. 370. 
2 “The Oil-Shales of the Lothians,” Mem. Geol. Sur., Second Edition, 1912, p. 10. 
3 It is interesting to note, as Mr Carruthers informs me, that in the Main Oil- 
Shale Field to the west, a marine band with goniatites and lamellibranchs has recently 
been found to occur in the heart of the Dunnet Group of oil-shales, 
