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THE CRETACEOUS ROCKS OF BRITAIN. 
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In the lower level 25 to 30 feet of creamv white blockv chalk 
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is seen, containing Am. [Acanth.] rotomagensis, Hplaster subglobosus, 
Hoi. trecensis, Pecten Beaveri , and other fossils. 
The most complete exposure of the zone of Holaster subglobosus 
is in the large quarry at Cherry Hinton, near Cambridge. The 
highest level of this shows the basal marl of the Act. plenus band and 
about 30 feet of tough blockv chalk, of a creamy white tint when 
damp but drying nearly white. In the middle stage of the quarry 
about 25 feet of rather hard white and yellowish-white chalk is 
seen, in which Holaster subglobosus is very common. The lowest 
level shows about 15 feet of greyish-white chalk overlying the 
Totternhoe Stone. 
The total thickness appears to be about 70 feet, and of this the 
upper 50 feet consist of white or nearly white chalk, which is 
more than usual ; lenticular bedding or jointing is developed 
in a very marked manner throughout the whole zone. 
Some 10 or 12 feet of the grey chalk overlying the Totternhoe 
Stone is exposed in the more southern quarries at Burwell, but the 
whiter chalk is not reached. 
There is a remarkable section in a quarry near West Bow, west of 
Mildenhall, in Suffolk, for the beds exposed differ from any elsewhere 
seen, and contain a band of red chalk like those of Lincolnshire. 
Melbourn Bock 
Grey laminated marly chalk ------ 
Hard compact and smooth white chalk, with Rhyneho- 
nella and Ostrea vesicularis ----- 
Soft laminated marly chalk - - - 
Blockv white chalk - - seen for 
Belem- 
nite 
Beds. 
The complete section visible here in 1886 was as follows : — 
Chalky soil - . 
Bough yellowish chalk, weathered - 
Bed marly chalk, brick-red at top, lighter red below 
Greyish-white chalk, marly and platy, containing lenticular 
lumps of hard chalk - -- -- -- - 
[ Hard grey rocky and nodular chalk 
Soft grey marly chalk -------- 
Very hard grey nodular chalk (Am. [Haploeeras ] Austeni, 
Actinocamax plenus, and Terebratula semiglobosa ) 
Thin-bedded whitish chalk ----- 
Hard greyish chalk ------ 
Softer thin-bedded chalk ( Holaster subglobosus ) 
Hard lumpy yellowish rocky layer 
Softer chalk below, according to the workmen. 
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On the eastern side of the quarry, near the entrance, the dip is 
westward, but the beds soon become horizontal. Owing to the 
flatness of the country and the paucity of exposures it is impos¬ 
sible to be sure of the exact horizon of these beds, but it is certain 
that they lie somewhere between the Totternhoe Stone and the 
