ZONE OF HARPOCERAS SERPENTINUM. 123 



Detailed description of the Saltwick Section. 



No. 1. Sandstone rock belonffina; to the Lower Sandstone series. . „„ . 



^ ^ ^ 60 feet 



J' 



2. Alternating beds of sandstone and shales, with remains of plants, chiefly Zamiacece. 



3. Rough ferruginous Dogger in Inferior Oolite, with inconstant bands formed of harder, more 



ferruginous, irregular, spheroidal masses of rock, 4 feet thick. 



4. Grey alum-shale, the upper part a little sandy, with few or no fossils. At about 5 feet in depth 



layers of small limestone nodules appear, and continue for about that space in sufficient plenty 

 to be worked for the making of "cement." Lower down the nodules are fewer, and admit of 

 a larger proportion of carbonate of iron, alumina, and silica. The shale is pyritous, and 

 abounds with fossils, as Harpoceras bifrons, Stephanoceras commune, Belemnites Voltzii, Leda 

 ovum, Gresslya donaciformis. Thickness 34 feet. 



5. A conspicuous, irregular band, occasionally swelling out into lumpy masses, more calcareous than 



most of the hard layers that occur below. 



6. Dark alum-shale, 34 feet thick, with an irregular band of nodules. This bed is not rich in 



fossils, and appears to be the lowest bed worked for alum. 



7. Is a thin flat bed of ironstone, somewhat remarkable for its continuity, 4 inches thick. 



8. Dark alum-shale, 16 to 18 feet thick, somewhat harder than the strata above. The fossils are 



chiefly Belemnites, of which a kind of bed is formed 3 feet below No. 7. There is also 

 another bed of Belemnites 1 foot from the bottom ; both are of limited extent. Monolis sub- 

 striatus. 



9. An irregular, frequently double band of subcalcareous nodules, large and small, lumpy, 



spheroidal, or flattened, |^ to 1 foot. 



10. Dark firm shale, 16 to 18 feet thick, poor in fossils ; Belemnites occur near the top and bottom. 



11. Hard, dark, reddened sliale bed, occasionally changing to a ferruginous band, 3 to 6 inches 



thick. 



12. Hard dark shales, 12 feet thick, containing Belemnites subtenuis, Inoceramus dubius. 



13. Band of remarkable flattened spheroidal balls. 



14. Hard dark shales, 20 feet thick, with numerous fossils, often pyritized, Harpoceras Mult/ravium, 



Belemnites tubidaris, Inoceramus dubius, Extracrinus Phillipsii, Wright. 



15. Band of irregular balls, pyritized. 



16. Hard grey shales, 20 feet. 



17. Jet-rock, hard shale, 10 feet thick, with calcareous concretions and considerable portions of Jet. 



Belemnites tripartitus, Aptijchus, &c. 



18. Hard shales, with large nodules in the upper part, 20 feet. 



19. Stephanoceras annulatum bed of nodules. 



20. Soft shales, 20 to 30 feet thick, and containing Belemnites cylindricus. 



