S. P. Woodward—WNature and Origin of Banded Flints. 149 
Cliff. The surface was much varied with ‘ pot-holes,’ ranging 
from 5 feet wide and 20 feet deep to one of 30 feet across 
and 40 feet deep. The Chalk, where not disturbed, was very 
solid, with layers of flints about 5 feet apart. The vein with 
banded flint was slightly inclined with a drop, on the down-cast 
side, of about 2 feet. Hight to ten feet lower than the banded 
flint, and about 25 feet from the surface, there was a course ot 
very compact yellowish chalk, about 3 feet thick and as hard as 
Portland stone; it was perforated with holes, as if by the 
Pholas, 1-14 inches wide, through which water seems to have 
percolated; and 10 feet below this was a layer of flint not more 
than 3 to } inch thick, as evenly laid and horizontal as a flag- 
paving, extending for more than a hundred feet through the 
cutting. 
EXPLANATION OF PLATES VII. AND VIII. 
Prats VII. 
Fig. 1. Broken section of flint containing a Ventriculite; the upper part 
solid, but the branched root forming cavities in the stone. 
(Mr. Wetherell.) 
2. Small flint pebble containing a segment of a fossil sponge (Cepha- 
lites), still showing the labyrinthic wall and angular meshes of 
sponge-fibre. (Muswell Hill, Mr. Wetherell.) ; 
3. Thin slice of a translucent yellow flint, containing a flexuous tube, 
filled up with curved deposits of similar flint, and containing 
strings of ‘oviform bodies’ (0) in its upper part. (Finchley, 
Mr. Wetherell.) 
4, Small fragment of black flint, with similar tube and bands. (Finchley, 
Mr. Wetherell.) 
. Section of pebble, containing a Sponge enveloped by an irregular 
discoloured space, through which and the Sponge itself the bands 
of subsequent infiltration have passed. (lent, Mr. Wethevell.) 
6. Fractured surface of a small black flint, with a tubular drusy cavity. 
bordered by coloured bands. (British Museum.) 
. Flint pebble, much waterworn, and corroded by the weather; one 
portion showing ordinary flint ; the other corrugated and resem- 
bling a Hamite. (Muswell Hill, Mr. Wetherell.) 
8. Polished section of a black Chalk-flint, from Gravesend, presented 
to the British Museum by the Rev. Norman Glass. The axis 
of the banded portion is stained with dark streaks, and contains 
an angular fragment of Jnoccramus (7). 
Prate VIII. 
Fig. 1. Broken section of a flint-pebble, containing a Ventriculite, the 
whole zoned with coloured bands. (J*inchley, Mr. Wetherell.) 
2. Black flint, with thin plate or vein of white flint running through 
it, bordered on each side by a discoloured and banded space. 
(Finchley, Mr. Wetherell.) 
3. Similar flint, with more simple fracture. (Finchley, Mr. Wetherell.) 
4, Fragment of black flint from Dover, containing vein of banded 
flint and Chalk. 6. Black flint. g. Grey flint. c¢. Chalk. 
On 
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