426 THE CRETACEOUS ROCKS OF BRITAIN. 
In the Cerne Valley the Middle Chalk occupies a narrow band 
on the steepest paid of the slope on each side of the valley from 
Nether Cerne northwards. It rises gradually to higher levels 
till it comes to form the upper part of the high ridges which form 
promontories on both sides of the northern entrance to the valley. 
Here, however, its surface is concealed by the overlap of the Clay 
with flints. 
Its thickness is still about 100 feet, and the hard rocky beds at 
its base and summit can be readily traced along the valley sides, 
but exposures of any depth are few. The lowest beds can be 
seen in the quarries on Giants Hill near Cerne, but are much 
weathered and pai tly covered by talus. At the base are 4| feet 
of smooth streaky yellowish-grey chalk, hard at the top but 
softer below. This is succeeded by beds of rough whitish 
and somewhat nodular chalk, alternating with bands of soft 
grey mail enclosing small lumps or nodules of white chalk, 
the harder beds average 18 inches in thickness, the marl beds 
from 3 to 12 inches, and the whole is between 7 and 8 feet thick 
overlain by white chalk, which breaks into small angular pieces. 
In the valley of the Frome the basset surface of the Middle Chalk 
forms a continuous tract along the eastern side from the hill above 
Frome St. Quentin to Crockway, between Maiden Newton and 
Frampton. Its thickness here is less, not more than 80 feet inter¬ 
vening between its base and the lowest bed of Chalk Rock. 
It forms a similar narrow band on the flanks of the hills south 
and west of Maiden Newton, running into and all round the Wyn- 
ford and West Compton Valley. 
At Crux ton the lower beds are exposed in two small pits south 
of the farmstead. The lower one shows the following beds: — 
feet. 
Hard white chalk, weathering into large lumps, but not 
nodular. -----3 
Layer of soft marly chalk, about 4 inches. 
Hard nodular rock, weathering into nodular lumps, some 
of which are green-coated - - - 4 
Hard nodular rock, with Rhynchonella Cuvieri , marked 
off by divisional planes above and below - - - 3| 
Hard rocky chalk, with a few green-coated nodules - 1 
Hard white blocky chalk seen for - 7 
The two beds of nodular rock (74 feet) seem to represent the Meb 
bourn Rock. Thinking the soft grey Belemnite marl could not be 
far below the floor of the quarry, I had a hole sunk, but this was 
dug feet in hard white chalk without reaching it. At 2 feet , 
dowm the base of a bed was nodular and had some fossils, Rhyn¬ 
chonella Cuvieri and an obscure fragment of an Ammonite, but 
nothing which was conclusive as to the zonal horizon of the 
material. There is here more than 13 feet of firm bedded white 
chalk below the nodular chalk of the Rhynch. Cuvieri zone. 
The upper pit is a shallow one, only showing about 6 feet of 
yellowish nodular chalk with Inoceramns mytiloides. 
