46 
THE CRETACEOUS ROCKS OF BRITAIN. 
Zone of Ammonites varians. 
Chloviiic Marl. The more sandy part of the sub-zone of Staur- 
onema does not extend far in from the coast. Mr. Topley observes 
that “ 10 feet of rather clayey and calcareous Greensand are exposed 
in the cutting just east of Folkestone Junction Station, at the west 
end of Martello Tunnel; there is soft Chalk Marl above, with a few 
green grains in the lower part. In the heaps of earth above the 
tunnel-mouth much Greensand may be seen, some hard and with 
nodules.”* 
It is seen again at the foot of Castle Hill in the most easterly of 
the roads which unite there and just north of their junction, but Mr. 
Topley states that “ it is here only 3 or 4 feet thick, and contains 
many small pliospliatic nodules.” 
West of this point the Stauronema zone appears to thin out 
entirely, for Mr. Simms, Writing in 1844, says it does not occur at the 
foot of Tolsford Hill, “ the only trace of it being some grains of sand 
mixed with the Chalk Marl over the Gault; ” + and Mr. Topley 
says, “ still further west, as in the road north of Stanford, I have 
not been able to find any.” (Op. cit., p. 154.) 
It is rather remarkable that a bed which is so conspicuous 
at Folkestone should thin out so rapidly; for in most other parts 
of the south of England it is a fairly constant band. 
We did not find any exposures of the base of the Chalk between 
Wye and Aylesford, but a note bv Prof. T. McK. Hughes, quoted by 
Mr. Topley, l states that a thin bed of dark Greensand occurs above 
the Gault near Charing, that such material was turned out of some 
deep drains east of Charing and was again touched near Eastwell 
In the brickyard at Aylesford, north-east of Maidstone, there is a 
thin bed of sandy glauconitic marl at the base of the Chalk (see 
section given in Vol. I., p. 88). The same bed is also seen in the cut¬ 
ting made for the tramway leading from the Burham brickyard to 
the large quarries in the Chalk half a mile east of Burham. It is not 
certain, however, that this bed really represents the zone of Stauro¬ 
nema Garteri, as that fossil has not been found in it. 
The outcrop of this glauconitic marl forms a low ridge 
in the bed of the river Medway between Burham and Snodland, but 
is only visible at low water. 
Further west it can be seen in the right bank of the watercourse 
issuing from a spring at Coney Hall Farmstead, half a mile south of 
Birling House. From this point to just east of Kemsing it is hidden. 
Immediately west of Kemsing it begins to regain importance, and 
becomes still thicker to the westward. 
“ Green marly sand below the Chalk ” was seen by Mr. Topley 
in the railway cutting south of Otford. At the spring-head near 
New Barns Farmstead, about a mile W.S.W. of Otford Church, 
* Geology of the Weald, Mem. Geol. Survey, 1872, p. 152. 
t Proc. Geol. Soc., Vol. iv. p. 206. 
I Geology of the Weald, Mem. Geol. Survey, 1872, p. 152, 
