496 
THE CRETACEOUS ROCKS OF BRITAIN. 
Metres. 
co 
55 
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hO 
* 
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+-> 
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<U 
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lO 
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I O 
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fHard and heavy limestone, perforated with tabules, 
many Echinoconus subrotundus, and Ter. semi- 
globosa -------- 
Greyish marly chalk, with Ech. subrotundus , Inoc. 
labiatus, Rhynch. Cuvieri, etc. ; flints rare 
Soft white marly chalk, alternating with beds of 
hard greyish compact chalk - 
\ Greyish marly chalk, with Ammonites nodosoides 
and large Inoc. labiatus - 
Greyish marly chalk, with some white nodnles, 
Am. catinus, Inoc. labiatus, and fish remains - 
Thin continuous seam of flint - 
Hard compact chalk, becoming nodular, and pass¬ 
ing down into a hard and heavy nodular chalk, 
\ Inoceramus labiatus and Cidaris hirudo - 
•50 
6*00 
1'85 
2*50 
3*50 
•02 
2 
i 
39-97 
rt 
The hard nodular rock at the base is evidently comparable with 
our Melbourn Rock, and it rests on the grey marly chalk identified 
by M. Bucaille as the zone of Belemnites plenus. M. Lennier, how¬ 
ever, does not separate the zone of Ter. gracilis , as at that time it 
was included in the zone of Inoc. labiatus ; and I am responsible 
for the grouping above suggested. The zone of Holaster planus is 
exposed in another quarry near the top of the hill, and there is 
supposed to be a depth of twenty to thirty metres between the 
two sections, this being occupied by the rest of the Terebratulina 
zone. If this is correct, the total thickness of the Turonian here 
will be over 200 feet. 
At Villequier, lower down the Seine, the thickness of these beds 
is much reduced, and is said not to be more than twenty-five or 
thirty metres (less than 100 feet), but possibly the whole depth 
is not exposed, for their thickness at Fecamp on the coast to the 
north-west is given by Hebert as 45 metres, * and he divides it into 
two portions, a lower portion comprising the hard beds with 
Echinoconus subrotundus (9 metres), and an upper portion, in which 
Rhynchonella Cuvieri and Spondylus spinosus are abundant (36 
metres). Here therefore the two zones have a combined thickness 
of nearly 150 feet. They can be followed westward in the cliffs 
as far as Etretat, where the beds are broken by faults, but appear 
to be at least 30 metres thick; thence they can be traced to St. 
Jouin, where the lower zone crops out at the top of the cliff. 
Here the thickness of the Turonian is given as only 12 metres, 
but probably this only refers to the portion which is visible, all 
the higher part having been removed by detritive agencies. 
The country to the south-west of Rouen has not yet been much 
explored by French geologists, and the surface of the chalk is for 
the most part covered by a thick mantle of Clay-with-fiints, so that 
it is only in the valleys that exposures of chalk are found. In 
the Orne, however, near la Ferte Fresnel and TAigle, the lower part 
of the Turonian is exposed in many places, and the marly chalk 
*Bn11. Soc. Geo|. He Fra,nee, S<*r. 3, Tom iii. p. 519. 
