Vol. 63."] MARINE FAUNA IN THE BRISTOL COALFIELD. 453 



the dominant dip, has been constructed by the direction and under 

 the superintendence of Mr. J. McMurtrie, F.G.S. From this section 

 it was seen that a thickness of not more than 850 feet intervenes, 

 between the uppermost limit of the Carboniferous-Limestone Series, 

 and the grits penetrated at the end of the exploration-branch. If 

 the upward limit is carried to the top of the first ' Water-Stone,' 

 then the Millstone Grit will have an approximate thickness not 

 far short of 1000 feet. The uppermost limit of the Millstone Grit 

 might be carried still higher, to include the 13 feet 4 inches of 

 massive quartz ose grit which lies about 20 feet above the ' black 

 shale with plant-remains.' The black shale we look upon, how- 

 ever, as belonging to the Coal-Measures, owing to the included 

 plant-remains consisting of Lepidophyllum majus, Sigillaria, Neuro- 

 pteris, and Cordaites, all typical Coal-Measure forms. Taking the 

 top of the 34 feet 10 inches siliceous grit as the upper limit, then 

 the total thickness of the Millstone Grit at Ashton Vale will be 

 980 feet, being the 850 feet calculated by Mr. McMurtrie and 

 130 feet of strata passed through in the exploration-branch. 



IV. Detailed Section of the Strata, from the * Red Ash ' or 

 ' Little Vein ' to the end of the Exploration-Branch. (See 

 diagrammatic section, p. 452.) 



Thickness in feet inches feet inches. 



1. Eed Ash Coal. 



2. Quartzose grit, with fireclay above it: 



Fireclay 1 4| 



Quartzose grit 19 4 20 8| 



3. Coal. 



4. Shales and Sandstones: 



Quartzose grit, with iron-pyrites 4 1^ 



Dark-grey shale, with plant-remains 2 3 



Fireclay (crushed) 3 



Micaceous grey sandstone 7 6 



Micaceous shales, with grit-bands 18 9 



Mudstone, with colour-bands. 5 8 38 &% 



5. Marine Band: 



Black laminated shales (Lingula, fish -scales, 



and worm-burrows) ... 4 



6. Coal 1 



7. Shale 10 7 



8. Marine Band : 



Black micaceous shale (Lingula abundant) ... 1 9| 



9. Shales: 



Black laminated shales {Cordaites and 



ferns) 2 4 



Grey shale, with ironstone-nodules and 



plant-remains 6 4^ 



Hard black shale, with ironstone-nodules .25 11 1^ 



10. Coal. 'Gay's' Seam 2 6 to 1 8 



11. Shales and Mudstones: 



Fireclay 1 4 



Fine greyish -blue mudstone 6 



Mud stone with ironstone-nodules 28 



Fireclay with Stigmaria 7 6 42 10 



12. Smith's Coal , 1 



