15 
LOWER CHALK—GENERAL ACCOUNT. 
sand of tlie south of England/'* It was left for the present writer 
to show that it was really the basement bed of the Chalk Marl, and 
that as such it was newer than any paid of the Upper Greensand. 
This conclusion was arrived at in 1874, after a study of the relations 
of the several formations, Gault, Greensand, and Chalk, in the 
counties of Buckingham and Bedford,! and he then found that 
Mr. Whitaker, who had mapped parts of those counties for the 
Geological Survey, had formed the same opinion. 
One other deposit maybe mentioned which up to the year 1877 
had always been called “ Upper Greensand." This is the green sand 
and marl which overlies the Gault at Folkestone, and is the bed in 
which Stauronema Carteri was first found. Mr. F. G. H. Price, 
writing in 1877,! pointed out that the fossils of this bed do not 
represent the fauna of the Upper Greensand of the west of England, 
and he rightly regarded it as the basal part of the Chalk Marl, calling 
it the zone of Stauronema Carteri. We agree with him, and con¬ 
sider it to be the stratigraphical equivalent of the Chloritic Marl of 
the Isle of Wight, as already defined and restricted. 
The Chalk Marl has so long been used as a name for the lowest 
part of the Lower Chalk, wherever that is of a marly nature, that 
it would have been convenient to retain this name, if it were possible 
to define it so as to connote a definite subdivision of the formation 
even though it might not wholly consist of marly chalk. 
Where the Totternhoe Stone exists this can be done, because the 
base of that stone can be taken as the upper limit of the Chalk Marl, 
but this is not very satisfactory, for the following reasons. In the 
counties of Norfolk, Lincoln, and York, the beds consist 
principally of rather hard greyish chalk, and contain little which is 
lithologically “ chalk marl." Again, where the Totternhoe Stone 
is absent, as it is over the whole of the south of England, there is 
seldom any definite line which can be taken as the limit of the 
Chalk Marl, if this were regarded as a lithological subdivision, 
apart from any consideration of the distribution of fossils. 
The Totternhoe Stone is another portion of the Lower Chalk 
which has well-marked lithological characters, but does not extend 
all over England. It takes its name from the village of Totternhoe, 
near Dunstable, where it has long been worked as a building-stone. 
It is a rough-feeling grey chalk, looking and feeling as if it was 
very sandy, but microscopical examination has shown that this 
roughness is not due to the presence of quartz-sand, but to 
the large proportion of small bits of broken shell which it con¬ 
tains. Its texture is compact and even grained, so that it works as 
a freestone, and it lies in thick beds, so that large blocks can be 
raised and cut into any shape. At its base there is generally 
a layer of green-coated calcareo-phosphatic nodules, and small 
* On the Upper Greensand or Chloritic Marl of Cambridge. Proc. Geol 
Assoc., Vol. iii. No. 1 . p. 1 (1873). 
t See Quart. Journ. Geol. Soc., Vol. xxxi. p. 256 (1875). 
% Quart. Journ. Geol. Soc., Vol. xxxiii. p. 434. 
