Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/180

86 west of A; but I have no doubt that the fossiliferous gravels, A B, will be found to lie in a similar concavity to those at Grays and Crayford, where the Thanet sands and chalk have been exposed.

The material for the beds (e) and (d) seems to have descended from A, and to have been brought by land-floods, and contains bones, but no shells except derived ones. On the contrary, (b) is full of shells deposited quietly. Many of the species are extremely delicate, and are found quite as perfect as recent specimens; the two series of deposits are interstratified together at D, the eastern bed (b) being of fluviatile origin, and the western (d) being apparently of pluvial origin, and more due to land-floods.

The chalk below A in fig. 19, Erith, along the line A B, Plate VI., is 50 feet from the surface. The bottom-bed (b) shown in the section is false-bedded sand with a few veins of gravel. The Cyrena is very abundant between D and B in this sand (b). The mammalian remains are most abundant in the brick-earth beds (d).

These beds (d, d) dip near A at 25° E, then fall to 9°, 5°, and eventually dip 5° W. near B, forming a gentle curve. The covering bed (e) is 4 feet thick, and full of the Woolwich pebbles between B and D. It then changes its character, and contains only a few flints, but masses of the Woolwich shell-bed when it reaches A. The remains of this shell-bed occur through (b, c, d) and (e). The angles of deposition were observed both by Mr. S. Skertchly and myself in 1868, and the heights were measured by the former. Great removals of brick-earth have recently been made near A, so that the original section cannot be seen.

Fig. 18.—Section in Erith Pit. (Natural scale.)

Between B and C, Plate VIII., a long face of the Cyrena-sand-bed