88 
THE CRETACEOUS ROCKS OF BRITAIN. 
The Mass of the Lower Chalk. 
We will now give some account'of the principal sections in or 
through the Lower Chalk. 
It will be convenient to begin at the eastern end of the island, as 
the whole stage is well exposed in the cliffs near Culver Point. This 
section was measured by Mr. Strahan in 1889, and by Mr. Hill 
(for this Memoir) in 1897, and they differ little as to total thickness, 
but the subjoined account gives rather more detail than the older 
one : — 
Zone of ) 6 
H. sub- K 
(jlohosus 
\ 
{ 5. 
Zone of 
Am. 
varians. 
Soft bluish-grey marl (sub-zone of Act. plenus ) about 6 
Firm white chalk, breaking into a smooth fracture, 
in massive beds ; contains Holaster subglobosus, 
H. trecensis , Discoidea cylindrica - - - - 85 
Grey chalk in regular courses, weathering as ribs 
under the wash of the sea - about 45 
Bluish-grey marly chalk with harder courses of grey 
chalk, which weather out as strong ribs under the 
wash of the sea ----- about 40 
Soft bluish-grey marl, passing down into firmer 
sandy marl, with Plocoscyphia labrosa - about 15 
Harder bluish sandy marl, with masses of 
Plocoscyphia labrosa and some fragments- of 
brown phosphate— Am. [ ; Sc/iloenb ] varians , Serpula 
umbonata, and other fossils- - - about 12 
Chloritic Marl in four beds (see p. 83) - - 8 
About . 211 
No. 1, the zone or niveau of fitauronema Garteri, has already been 
described. Nos. 2 and 3 are the beds which Dr. Barrois terms the 
zone of Plocoscyphia mceandrina (—labrosa). These three beds, 
taken together, are the equivalents of Beds I. and II. at Folkestone. 
Beds 4 and 5 are those which have often been called “ the Grey 
Chalk,” but they do not possess any special palaeontological charac¬ 
ters ; Am. [Schl .] varians ranges from No. 1 into No. 5, and conse¬ 
quently all these beds fall into the zone of Am. varians. 
No. 6 is the massive white chalk already mentioned (see p. 82), 
and No. 7 is the sub-zone of Actinocamax plenus , though that 
fossil has not been found here. 
Another excellent section of nearly the whole of the Lower Chalk 
is to be seen in Mr. Munim’s quarry, 300 yards west of Yarbridge, 
which must have been deepened considerably since Mr. Strahan’s 
visit, since it showed the following succession in 1897 : — 
ft. in. 
Hard white bedded chalk, with Inoceramus mytiloides 
and Rhynchonella Cuvieri - - - more than 20 0 
Hard rough white nodular chalk, divided into 
thinnish beds by marly partings - - - 5 0 
Rough white nodular chalk - - - - - 1 6 
Greenish-grey marl - - - - - - -02 
Hard rough whitish nodular chalk, veined and 
streaked with greenish-grey 
4 0 
