GEOLOGISTS' ASSOCIATION.

ON SOME

SEOTIONS OF OHALKBETWEEN

OROYDON AND OXTEAD,

WITH

OBSERVATIONS ON THE CLASSIFICATION

OF THE CHALK.

BEING A PAPER READ BEFORE THE

GEOLOGISTS' ASSOCIATION, JANUARY 7, 1870.

BY

CALEB EVANS, F.G.S.

PRINTED FOR THE GEOLOGISTS' ASSOCIATION,BY GEO. P. BACON, SUSSEX ADVERTISER OFFICE, LEWES.

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ON SOME SECTIONS OF THE CHALK BETWEENCROYDON AND OXTEAD,

With Observations on the Classification if the Chalk.

Introduction. I purpose in the following paper to notice the

distribution of the organic remains met with in the chalk exposed in

the cuttings and on the embankments of a raIlway called" The

Surrey and Sussex Railway," which was commenced a few years

since in order to form an additional line of communicationbetween Croydon and Hastings.

In the early part of 1867 all work on the line was discon­

tinued, and since that time the railway has remained in an un­

finished state.

Commencing a little to the south of Croydon, the direction of

this railway is at first nearly parallel to that of the London,

Brighton, and South Coast Railway, and it traverses the minor

spurs and depressions which descend from the hills, forming the

eastern side of the valley in which the small village of Pm-ley is

situated. After passing, by means of a tunnel, under the high

ridge of Riddlesdown, it takes a south-easterly direction along the

eastern side of the valley leading to Caterham, as far as a spot a

little to the south of W mlingham Station, and then diverges more

to the eastward, and passes up a smaller valley until it reaches

the higher ridges connected with the escarpment of the North

Downs, where it enters a long tunnel and reappears in the neigh­

bourhood of Oxtead, in the valley occupied by the gault.

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4

The direction of the line (from a little west of north to a little

east of south) is nearly at right angles to the line of strike of the

beds of chalk constituting the North Downs of Surrey, and the

sections exposed in the various cuttings show in proceeding

from south to north the successive outcrop of higher beds of the

series, the dip of the strata being in general at a slight angle to

the north, although in a few instances it is in the opposite direc­

tion. In some spots the beds are much faulted.

The beds exposed on this line of railway do not include the

highest chalk of the district. A space, nearly a mile in length,

extends from the most northerly cutting on the line, to the spot

where the chalk disappears beneath the tertiary sands, and in this

interval higher beds than any seen on the railway probably rise

to the surface.

The junction of the chalk and the sands is seen in the cutting

of the Brighton Railway, between the stations of East Croydon

and South Croydon, and also iu a chalk pit by the side of the

lane leading from Croydon towards Shirley. The tertiary beds

cap some of the higher hills in the neighbourhood, but are not

exposed in the railway sections. The only deposit above the

chalk observed in these cuttings is a marly clay, with or without

flints, whkh is seen chiefly on the flanks of the higher ridges, and

is considered to be the result of the disintegration of the chalk by

sub-aerial action.

PURLEY BEDs.-(Cuttings 1, II., III., IV.)* The highest beds

of chalk exposed are seen in the cutting through the ridge up

which the road from Purley to Sanderstead ascends to the high

ground.

* See Sections. These sections are drawn on the horizontal scale of 600feet to an inch, and on the vertical scale of 200 feet to an inch: the dottedlines in the cuttings represent some of the most conspicuous bands of flints,and the continuous lines bands of yellow marl.

5

This cutting (No.1) is about 970 feet in length, and the direc­

tion is from N.E. to S.W., magnetic. The bands of flint seen

on each side have a slight inclination to the north or north-west,

but as they occasionally undulate, the precise angle of dip cannot

be determined. A good section is seen by the sides of a tem­

porary bridge, situated at the deepest part of the cutting. In

other parts the stratification is not so clear, the sides having

been smoothed down. The section at the bridge shows beds of

chalk, varying in thickness from about one foot to four feet, with

intervening bands of flint nodules and a thin vein of tabular flint,

and on the east side of this cutting, on the south side of the

Sauderstead Road, a thin vein of tabular flint is seen sloping

down at an angle of about 45° between beds of flint nodules.

The details of this section are given in the Appendix.

An examination of the surface of this section shows that

organic remains are not abundant in these beds. Many fossils

may be obtained from the chalk embankments, both to the north

and south of the {'utting, but it is probable that many of these

have been derived from the cuttings more to the south, which

have been connected with this one by embankments. The em­

bankment to the south of this cutting is about 700 feet long,

and as the beds, both in the cutting already noticed and also in

that to the south have a slight inclination to the north, it is

possible that a few beds of chalk rise to the surface in the low

ground between the two ridges, which are not exposed in the rail­

way section~.

The embankment is slightly curved, but the next cutting

(No. II.) has very nearly the same direction as th,e preceding

one. It is about 1,600 feet in length, and in the deepest part it

exposes about 25 feet of chalk with bands of flints. At about

250 feet from the south end, it is crossed by a lane leading past

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6

Purley House to Sanderstead. The clearest section is in the

unsmoothed surface near this lane. The details of the beds here

seen, consisting of alternations of beds of chalk with bands of

flint nodules, are given in the Appendix.

The greater part of the cutting to the north of the lane has

been permanently smoothed down, in consequence of which the

bedding is somewhat obscured, but the direction of the inclination

of the strata can nevertheless be determined. The more con­

spicuous bands of flints may be traced in the cutting for some

considerable distance, and show a general dip at a small angle in

a northerly direction. The minor undulations of these bands

render it difficult to determine the exact angle of dip.

This northerly inclination causes the beds seen in the section

at the lane to disappear at a considerable distance before the

north end of the cutting is reached. In that part they are

succeeded by beds which, owing to the smoothed and weathered

state of the surface are very obscurely exposed, but several bands

of flints, and an undulating band of marl are indistinctly seen, and

at the north end are two bands of flint, the inclination of which

corresponds with that of the surface of the hill. The upper one,

which consists of nodular flints, is covered only by about one foot

of rubble; the lower band is about one foot four inches below the

upper one, and is a thin band of tabular flint. This is the only

band of tabular flint seen in this cutting.

The most interesting deposits in this cutting are two beds of

chalk, separated by a band of flint nodules, and having a band of

large flint nodules above. These two beds contain many specimens

of 1lficraster cor-anguinum, together with other fossils, including

occasionally Ananchytes ovata. Although both these fossils

are met with in other sections of the chalk on this line,

Micraster cor-anguinum is nowhere found in so great abundance

7

as at this spot. The specimens from this band often contain in the

interior, and are coated externally, with a yellowish chalk, so hard

that it is extremely difficult to clear the fossils without chipping or

breaking the shell. It is probable that most of the fossils

obtained from the embankments to the north have been derived

from this fossiliferous band.

In the cuttings already noticed, the general dip of the beds is

to the north. After passing over the short embankment separating

the last described cutting (No. II.) from the next one to the south,

it is seen in the latter that the dip is at a very slight but quite

perceptible angle to the south, and that the intervening depression

occnpies the site of a fold, or minor anticlinal axis of the chalk.

This cutting (No. III.) is separated from the preceding one

by an embankment, about 300 feet long, which passes over the

grounds of Purley House. The cutting is about 400 feet in

length, and exposes a fine section, 38 feet in vertical depth. A

thick band of flints is seen near the north end of this cutting, at

the height of about fourteen feet. At the south end this band

is at the height of eleven feet, where it forms the roof of a small

tunnel which has been partly excavated. Micraster cor-anguinum

is present in the beds of chalk below this band of flints.

It appears that there is in this cutting a vertical section of all

the beds seen in the second, or Purley House Lane cutting, and

probably of a few feet of the beds both above and below them.

Thus, in this section above the conspicuous band of flints before

noticed, there are appearances of three or four bands of flint

nodules, and of a yellow band of marl, and near the top of the

section a very conspicuous band of tabular flint is seen, and

another band of flint nodules a little distance above it. These

details correspond very closely with those less clearly seen in the

section towards the north end of the second cutting, and show

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8

that there is at this point a true fold or anticlinal axis of the

beds.The three cuttings already noticed are all connected together

by embankments formed of the excavated chalk. Although many

fossils are exposed on the sides of the cuttings in the beds in which

Micraster cor anguinum abounds, the embankments afford the

greatest facilities for forming a collection of the organic remains

of this part of the chalk. It is not possible to determine the

precise position which these scattered fossils occupied when in

situ; but it is probable that the majority of them were derived

from the Micraster band, although some may possibly belong to

the higher and less fossiliferous portion of the chalk exposed.

In considering the distribution of the fossils of the chalk it

becomes therefore necessary to group together the chalk exposed

in these three cuttings. These beds, together with the smallportion

possibly concealed in the depression between the cuttings I. and

II., would amount to about 65 feet in thickness, and show a well

marked fossiliferous band in the lower part. For convenience of

reference I have named this group of deposits "The Purley

Beds," as the three cuttings are all adjacent to the small village

of Purley.

The southernmost cutting, before described, has not been com­

pleted, and on the southern side of the ridge little has been done

except the removal of the turf. This process has exposed a

very interesting condition of the subsoil. The surface is covered

with broken but perfectly angular flints. The broken and

bleached characters of these flints are the result of the sub-aerial

denudation to which the chalk has been subjected.

The uncut portion of this ridge is about 700 feet long,' and

is succeeded to the south by an embankment about 1,200 feet in

length, which curves slightly from a south-westerly to a south-

9

easterly direction, and is wholly formed of chalk derived from

the cutting next to be described.

This cutting (No. IV.) has been excavated in the northern

slope of the high ridge known as Riddlesdown, and ends at the

temporary mouth of the tunnel under that hill. It is 638 feet

in length and 35 feet in depth at the southern end by the mouth

of the tunnel; the greater part has been smoothed down, in con­

sequence of which the .tratification is to a great extent concealed,

The superficial deposit is in this spot of greater thickness than it

is on the low ridges to the north, and consists of a reddish brown

clay containing many broken flints, below which is brown marly

or sandy clay, resting on the chalk with an irregular line of junc­

tion, and filling hollows in the upper part of the latter bed. On

the adjacent embankment there are a few blocks of chalk having

on one surface irregular shallow cavities. These cavities have

perhaps resulted from atmospheric agencies acting on the chalk

immediately below the superficial beds.

A tolerably clear section is seen at the south end of the cut­

ting, adjacent to the mouth of the tunnel, and shows beds of chalk,

each about three feet thick, alternating with bands of flint

nodules.*

The beds in this cutting dip slightly to the north. Those in

the cutting No. III. dip at a very small angle to the south, thus

forming a trough shaped arrangement of the beds.

In the section seen in this cutting there are no strongly

marked characters serving to identify this chalk with that of the

preceding or Purley sections; but by carefully noting the dis­

tribution of the various fossils scattered on the embankment,

some conclusion can be arrived at with regard to the position

which they occupied when in situ.

1I See Appendix.

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10

In forming an embankment from material removed from a

cutting, the debris from the highest part of the cutting and from

the part nearest to the embankment must be deposited at the

end nearest to the cutting, while the material from ~xcavations

deeper in the hill and lower in the cutting would be found at a

greater distance.In this instance at a single spot on the embankment, not far

from the end of the cutting, Micraster cor-anguinum is present

in considerable abundance. On other parts of the embankment

it is by no means so plentiful. In the lower part of the cutting

itself very few specimens are seen. From this circumstance the

conclusion may be drawn that a bed abounding in Micraster is

present in the upper and obscure portion of the section, and this

is the precise position in which, judging from the dip of the

beds, the Micraster band of Purley might be expected to appear.

This inference is further confirmed by the fact that on the spoil­

heap around a shaft, sunk at a very short distance above the tunnel

mouth and passing through the same beds as those seen in the

section, this Echinoderm also abounds.

Further to the north along the embankment the most abun­

dant organic remains are fragments of a large species of Inocer­

amus (I. Cuvieri). These would, for the reasons before stated,

be derived from beds slightly lower in the section than the

Micraster bed; this shell is also common on the spoil-heap of

the shaft before mentioned.

It appears, therefore, that thu Micraster band of the Purley

beds is present in the upper part of this cutting, below which

are beds with Inoceramus Cuviel'i, and at the base of the section

a few feet of chalk, probably lower in the series than the beds

seen in the Purley cuttings. The whole section and the whole

group of fossils derived from it so closely approach to the sec-

11

tion and fossils of the Purley chalk that these beds must also be

assigned to that horizon.

As however the cutting and embankment are disconnected

from any others I have appended a separate list of fossils."

The cutting last noticed ends towards the south at the mouth

of a tunnel under the high ridge of Riddlesdown, and the beds

are concealed for a distance of about 2,800 feet.

To aid in the construction of this tunnel, three shafts have

been sunk from the surface of the hill, and from the spoil-heaps

around these shafts many fossils may be obtained. The most

northerly of these shafts is immediately above the north mouth

of the tunnel. About half-way up the northern slope of the hill

there is another shaft, and a third is situated at the highest part

of the hill.

The shafts necessarily pass through all the beds composing the

hill until they reach their extreme depth. It is, therefore, diffi­

cult, if not impossible, to determine the precise position which the

fossils found on the spoil-heaps occupied when in situ, and this

fact renders any organic remains obtained from this spot of little

value in an attempt to determine the range and distribution of

life in the chalk.

UPPER KENLEY BEDS.-(Cutting No. V.)-It is frequently

the practice in constructing railway tunnels to form a temporary

cutting and a temporary mouth, and afterwards to cut the ground

further back beyond such temporary mouth to the spot where the

permanent mouth will be situated.

The southern end of the Riddlesdown tunnel is at present in

this condition: there is an upper cutting in the slope of the hill

about 50 feet deep and about 400 feet in length, within and below

* See page 30.

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12

which, at a distance from the north end of 188 feet, is the tempo­

rary mouth of the tunnel, and a lower cutting about 30 feet deep

extends 350 feet from this spot.

A slight inclination of the beds to the north is seen both in

the upper and lower cutting. The upper one has been smoothed

down, bnt shows beds of white chalk with bands of flints. The

chalk in this upper cutting has become rubbly from the action of

the weather, and the bands of flints are very imperfectly seen.

The most conspicuous features are two bands of chalk or chalk

marl, of a yellow colour, which rise gradually towards the south.

Of these bands the upper one is at the height of 16 feet above

the base of the upper cutting at the northern end, and it there

contains concretions of iron pyrites. From this point the band

undulates slightly, but becoming straight, outcrops at the surface

at 220 feet from the north end, at the height of 24 feet. The

lower yellow band is about 15 feet below this one, and is parallel

to it in direction.

The only fossils I have noticed in this upper cutting are a few

specimens of Micraster cor-anguinum.

The lower cntting by the temporary ~outh of the tunnel is

still in a rough state, and presents a fine section, showing beds

of chalk with intervening bands of flint nodules, and in the lower

part two bands of tabular flint. The bands of flint are more

crowded together here than they are in the Purley group, very

few of the beds of chalk exceeding two feet in thickness.

Immediately within the tunnel mouth on the east side a fault is

seen which throws down the beds at least 1 fooL 2 inches towards

the south. The direction of this fault is from S.W. to N.E., and

it may be well seen above the centre of the tunnel mouth, and

also on the west side of the cutting; this fault probably gives

rise to the undulations of the yellow band in the upper cutting.

13

In the beds immediately above the tunnel mouth one side of this

fault is exposed, and presents a very remarkable example of the

rubbed surface known as "slickensides." The grooves and

ridges in this instance are in a horizontal and not vertical direc­

tion, denoting a lateral shifting of the beds in addition to the

vertical displacement.The direction of both the upper and lower cuttings is very

nearly north and south.The lower cutting has afforded to me a rather plentiful supply

of fossils, many of which have been ohtained in situ.

The beds immediately above the tunnel mouth contain many

specimens of Micraster cor-anguinum, but in the lower beds of the

cutting, although this fossil is by nomcans uncommon, Ananchytes

ovata appears to be the most abundant Echinoderm, and is asso­

ciated with Spondylus spinosus.

The relation of the chalk in this cutting to the beds exposed to

the north of Riddlcsdown is not clearly seen. If there are no

faults or undulations in the concealed part of Riddlesdown the

slight northern dip of the beds seen in the cutting at the north

mouth of the tunnel would cause them to crop out on the south

side of the Down at a considerably higher level than the line of

railway. A bed of chalk in the lower cutting abounds with

Micr-aster cor-anguinum. At Purley the beds below the Micraster

band contaiu Inoceramus Cuvieri in abundance. In the southern

cutting this shell is rare, .and beds abounding with Ananchytes

ovata, associated with Spondylus spinosus, appear below the

Micraster bed. It may therefore be inferred that the beds at the

south mouth are distinct from and probably lower in the series

than the Pudey beds.The south mouth of the tunnel is situated at a short distance

from the Kenley Station on the branch railway to Cater-

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14

ham, and immediately below the Kenley Rifle Range, and for

facility of reference I have adopted the name of this village to

distinguish this part of the chalk; but, as the next section of the

chalk to the south (which shows a very different group of fossils)

is also nearer to this village than to any other, I have applied to

the chalk in the last described cutting the name of the" Upper

Kenley Beds."

An embankment about 1,100 feet in length skirting the side of

Riddlesdown, and curving slightly towards the south-east, sepa­

rates the section of the Upper Kenley beds from a deep and very

interesting section of beds of chalk, which, as they bear a certain

relation to those last noticed, but at the same time present very

important differences, I have named the" Lower Kenley Beds."

It is possible that in the course of this embankment beds,

intervening between those exposed in the cutting by the south

mouth of the tunnel and those seen in the cutting next to be

noticed, may rise to the surfacewithout being exposed in the cut­

ting. As the northern inclination of the beds is but slight, the

concealed portion would be of but small thickness.

LOWER KENLEY BEDs.-(Cutting No. VI. )-The cutting now

to be described is about 1,120 feet long, the direction being

N.N.W., and it is crossed about the middle by a road leading

from the top of Riddlesdown to the Rose and Crown Inn in the

Caterham Road. The temporary bridge, by means ofwhich the

road passed over the cutting, has been filled up, thus dividing

the cutting into two nearly equal portions. The portion on the

north side of the road is not more than 25 feet deep, and has been

to a great extent smoothed down. In this part there do not ap­

.flear to be any conspicuous bands of flints, but many remarkable

flints are dispersed· throughout the mass. These flints are nearly

15

all cylindrical in shape, and on being split. show a tubular cavity

containing a cylindrical core of flint, which is covered and the

cavity in the outer flint is lined with the white powder frequentlymet with in the interior of flints which have been formed around

sponges. Sponge flints of various forms are very common both in

the Purley chalk and the Upper Kenley chalk, but it is at this

spot that these cylindrical sponge flints are most abundant.

There are also seen in this part of the cutting one or two marly

bands, but owing to the rubblyand weathered state of the surface

the stratification is not clear.

To the south of the road over the railway the cutting has been

excavated deeper into the hill, and exposes on the eastern side a

section about 80 feet in depth.

The higher portion of this part of the cutting shows the beds

with cylindrical flints; but as this part has been smoothed

down and cannot, owing to the steepness of the slope, be easily

examined, no details can be given. There is no appearance of

conspicuous bands of flint in these beds.

Towards the south end of the cutting a clearer section is

seen, exhibiting in the lower part beds of chalk, alternating

with bands of flint nodules, several of which bands consist of

nodules of very large size. The thickness of the intervening

beds of chalk is greater than that of the Upper Kenley beds,

amounting in some instances to four feet.

The general inclination of the beds is towards the northern

end of the cutting, but the bedding is by no means regular, and

at one spot there is a very sharp curve down of the beds toward"

the south. The details of this cutting will be found in the Ap­

pendix.Several of the beds of chalk in this cutting contain numerous

fossils. The characteristic fossils are two Echinoderms, viz.,

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Holaster (or Anancltytes) planus and Micrastel' cOI·-hovis. Both

ofthese are tolerably plentiful in the middle portion of this section.

The ouly other spot from which I have obtained Holaster planus

is the spoil-heap at the top of Riddlesdown, whence I have ob­

tained several specimens; but the position which these occupied

when in situ is not clear. I have not detected lJficraster cor-hovis

in any other part of the chalk.·

In the lower beds of the cutting a small species of Cypltosoma

is abundant, and also specimens of a large Inoceramus.

The" Lower Kenley Beds" appear to be at least 80 feet in

thickness.The cutting (No. VI.) has not been completed at the southern

end, and an uncut portion of the hill, about 320 feet in length,

separates it from the large chalk pit opposite the Rose and

Crown Inn, which at present interrupts the continuity of the

railway line.This pit is at least 150 feet in height, and shows most of the

beds seen in the railway sections to the south of Riddlesdown.The chalk with bands of flints occupies about two-thirds of the

section. In the upper part the bands of flints are crowded to­

gether at small intervals, as is the case in the Upper Kenley

beds. In the middle part the bands are more distant, and the

individual flints are often of large size; this group is evidently

the extension of the Lower Kenley beds seen in the last cutting.

The lower part of the section shows beds of white chalk with­

out any regular bands of flints, but containing in the upper por­tion a few dispersed flints.

It may be noted that Mr. Whitaker in his paper on the Chalk

, I have obtained one specimen of this fossil from cutting No. XL, where,as will be seen, the lowest part of the chalk with bands of flints forms theupper portion of the section.

17

Rock of Berks, &c.,· states that Mr. Drew had noticed the chalk

rock in this locality; this rock is described as "hard blocky

chalk, jointed perpendicularly to the plane of bedding; with lines

of irregularly shaped hard calcareo-phosphatic nodules, which

are green outside but cream-coloured within; it breaks with an

even fracture, rings when struck with the hammer, and is of a

pale cream colour, the nodules darker than the rest."

WHITELEAF BEDs.-(Cuttings Nos. VII., VIII., IX., X.,XI.)-The cuttings to the south of the Rose and Crown pit for

the distance of about one mile and a quarter expose a compara­

tively small thickness of chalk, in consequence of a considerablefold or anticlinal axis of the beds, and the chalk of these cuttings

presents but one well marked fossiliferous bed.

The only group of houses in the immediate neighb:mrhood of

these cuttings is at a spot known as Whiteleaf. I have there­

fore distinguished these deposits as the" Whiteleaf Beds."

Separated from the chalk pit by a few feet of ground un­

touched is a shallow cutting (No. VII.) 440 feet in length on

the east side. It is on this side cut to the depth of 30 feet, but

it is very short and not more than three feet in depth on the

west side.From the slight inclination of the beds seen in the chalk pit

and in the cutting to the north it might be inferred that the

lowest bands of flints would be exposed in this cutting. The

sides, however, are so completely smoothed down, weathered,

and in places covered with superficial debris that no details can

be seen. I have not obtained any fossils from this cutting or

from the embankment, about 200 feet in length, which separates

it from the next.

.. Quart. Journ. Geo. Soc., Vol. 17.

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18

The next cutting to the southward (No. VIII.) is alsosmoothed down. It is 560 feet in length, 33 feet deep on the eastside, and 6 feet on the west. The direction of the cutting is nearlynorth and south. The section consists of white chalk, with a veryfew dispersed flints, but no regular bands. These flints in manyinstances contain the remains of sponges, or show fragments ofshells embedded in them.

Towards the north end there are indications of a band ofyellow marl, but this can only be traced for a very short distance.Near the middle of the cutting a bed of chalk, containing num­erous remains of Inoceramus Brongniarti, is present, but is soindistinctly seen that the thickness and inclination of the bedcannot be here determined. On the embankment (360 feet long)formed from the chalk of this cutting this fossil is abundant,

several specimens being often crowded in single blocks, showingthat there is here a well marked fossil-bearing bed.

The Echinoderms, which are the most abundant and character­

istic fossils of the beds previously described, are here muchfewer in numbers, but specimens of Galerites albo-galerus varietysubrotundus are occasionally found.

A. valley, 1,700 feet in breadth, separates the last cutting fromthe next one.

The direction of the cutting (No. IX.) is slightly to the east ofnorth. It is about 830 feet in length, and on the westside 36 feet in depth, and slightly deeper on the eastside. The inclination of the beds is at a small angle towardsthe north. On the eastern side where the cutting remains in a

rough condition thick beds of white chalk are seen, having severalmarly bands in the upper part. There are no flints in this chalk;the few found in the cutting appearing by their colour to havebeen derived from a superficial deposit. The most interesting

19

features in this section may be observed on the western side.Near the northern end a well marked band of yellow marl6 inches thick is seen at a height of 8 feet. This band extendsfrom that spot for about 250 feet, where it is at the height of9 feet. A well marked fault, nearly vertical in direction, hereraises the marl band about 4 feet, as on the south side of the fault

it is at the height of 13 feet. From this spot the band is againcontinuous for a distance of about 56 feet, where it attains aheight of 15 feet. Here another well marked fault, having aninclination to the south, throws down the band for about 9 feet, ason the south side of this fault it is at the height of only 6 feet.

From this point to near the south end of the cutting the bandundulates, but has a general inclination to the north. It cropsout at a distance further south of about 200 feet, and at aheight of about 25 feet.

There are a few bands of marl above this thick one, which havealso been influenced by the same dislocations.

The fossils in this cutting are not numerous. I have notnoticed any in situ in the lower beds, but I have obtained from

the fallen blocks Ventriculites and fragmentary remains of fishes.A few blocks contain the remains of Inoceramus Brongniarti, andit is probable that the whole or a portion of the fossiliferous bednoticed in the preceding cutting is present in the upper part ofthis one. This inference is confirmed by the fact that this species

is also found, together with Galerites albo-galerus variety sub·

rotundus, on the embankment at the north end, which has beenformed from the de'bris of this cutting.

The hill through which the cutting (No. IX.) has beenexcavated is at the south end separated from the next ridgeby a narrow valley. A low embankment about 80 feet longhas been formed across this valley. The details of the cutting

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(No. X.) in the next hill show that the small intervening

valley is situated at the axis of the fold of the White­

leaf chalk. This cntting is 240 feet in leugth, about 36

feet in greatest depth, and has a direction nearly north and

south, and it has been excavated on one side only of the ridge.

It shows near the top a considerable thickness of rubbly,

weathered chalk, below which are two bands of yellow marl; the

lower about 6 inches thick.

The two bands seen in the preceding cutting show a northerly

inclination, but in the present instance the dip is clearly seen to

be towards the south.

With the exception of these bands of marl no clear lines of

bedding are seen in this cutting, which has not at the south end

been excavated to the full depth.

From the chalk of the higher part of this cutting I have ob­

tained specimens of Inoce,'amus Brongniarti and Galerites albo­

galerus variety sub,'otundus. The cutting is of too limited extent,

and too unfinished, to furnish a large and separate list of organic

remains. Much of the excavated chalk must have been deposited

on the embankment at the north end of the preceding cutting.

The southern slope ofthe ridge in which the cutting (No. X.)

has been made is covered by bushes, and for a distance of about

1,600 feet no works of the railway have been commenced, with

the exception of a very short cutting in the wood, exposing

about 12 feet of rubbly chalk.

The cutting in the next ridge to the south of this untouched.

interval presents a deep and extremely interesting section.

The total length of this cutting (No. XI.) is a little over 400

feet, but the southern part has not been wholly cut, platforms of

chalk at different levels remaining. The lower part has been ex­

cavated by means of a temporary tunnel. The direction of the

21

cutting is about N.N.W. The depth from the highest part of

the hill to the level of the railway is about 54 feet.

The inclination of the beds in this cutting is to the south-east,

and shows that the chalk is on the southern slope of the White­

leaf anticlinal; and as the cutting is at a considerable distance

from the central axis, it might be expected that here the higher

beds affected by this flexure would appear, and this view is very

clearly confirmed by the fact that in the upper part of this cutting

at least four well defined bands of flints are seen. These beds,

therefore, represent those exposed to the south of the Rose and

Crown pit. In this case they are more clearly seen in conse­

quence of the rough and unfinished condition of the cutting.

At about 12 feet from the top of this section is a well marked

band of yellow marl; a band of flint nodules is seen about 2 feet

below the marl. Another band of marl is seen about 8 feet below

the first, and another band of flints immediately below it. This

is the lowest band of flint nodules seen in this section.

The chalk below this band of flints is thick bedded, in some of

the beds amounting to 4 feet. This chalk contains, scattered

throughout it, isolated flints, nearly all of which enclose the

remains of sponges.

In the lower part of the cutting the lines of bedding are

numerous, and the beds of chalk arc thinner than is the case in

the upper part immediately below the chalk with bands of flints.

About 10 feet below the lowest bed of flint nodules there is a

bed of chalk of a nodular and concretionary character, with

ochreous markings, apparently the remains of sponges. This bed

may perhaps be the equivalent ofthe " chalk rock" of Whitaker,

but it is not here sufficiently well defined to form a definite

horizon in the chalk. Blocks of chalk of a similar character are

also seen in the next cutting to the north (No. X.)

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22

In the lower part of the cutting there is a bed about 2 feet

thick, which contains many specimens of Inoceramus Brongniarti.

Near the north end a slight fault is seen which slopes in anortherly direction, and throws down the beds of chalk for aboutone foot in the same direction.

The embankment formed from the chalk of this cutting is alsointeresting, as affording occasionally, in addition to Inoceramus

Bl·ongnial·ti, very fine remains of Sponges, and Ventriculites.

It would be interesting to trace the distance to which thesoutherly inclination of the beds, bringing in the chalk with flints,

extends. Unfortunately to the south of this spot a long space in­

tervenes where no excavations bave been made, with the exception

of a slight and unimportant cutting formed in a narrow depres­sion between the ridges j and the turf has been removed in a

few places.The cutting last described is situated at a short distance north

of the spot where the main Caterham valley divides and sends offan irregular lateral valley to the east and south-east. The

lowest part of this lateral valley is crossed by a viaduct of fourarches, and is at a distance of about 3,200 feet from the cutting(No. XI.) The intervening tract consists of the southern slopeof the hill in which the cutting is made, broken by the slightdepression already mentioned. The only evidence I have foundof the extension of the chalk with bands of flints over tbis spaceis the fact tbat at places, not far above the bottom of the valley,

broken and bleached flints, similar to tbose seen near Purley, areoccasionally exposed. It is considered that these shattered flints

are the result of atmospheric disintegration of beds of chalk andflints in situ, and it is therefore probable that the chalk with flints

extends, or did extend, on the northern slope of this valley,

nearly to the lowest point.

23

It will be seen, when the cuttings to the south of this valley

are described, that the chalk exposed in them is lower in the series

that the Whiteleaf beds, and much below any chalk with flints.

It may therefore be concluded that this lateral valley occupies

the site of a considerable fault, which brings the chalk with flints

into contact with the lower beds of chalk without flints.

The cuttings and the tunnel to the south of this valley pass

through or adjacent to Marden Park, the grounds of which

extend nearly to the escarpment of the North Downs. I have

therefore distinguished this part of the chalk as the Marden

Park beds, and r"have considered it desirable to form an upper

and a lower subdivision.

UPPER MARDEN PARK BEDS.-(Cuttings Nos. XII. and XIII.)

These cuttings are of no great depth. The first (No. XII.) is

immediately above the southern slope of the lateral valley. It

has been smoothed down, is 500 feet in length, from N.N.W. to

S S.E. in direction, and is about twenty feet in depth on the

eastern side, and slightly deeper on the west.

At the top of the cutting there is a considerable amount of

reddish brown marly clay resting on the chalk, with a very

irregular line of junction. The chalk of the cutting is very

rubbly and weathered. The only feature of interest is a band of

marl which, at the distance of 240 feet from the south end is at

the height of ten feet, diminishing in height in the next 200 feet

to five and a half feet, thus denoting a well marked inclination

of the beds towards the north. I have found no organic remains

in situ in this cutting. The position in the series of the chalk of

this cutting cannot be accurately determined, but it is probably

clDsely connected with the chalk .of the cutting next to be

described.

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24

To the south of this cutting is a high embankment, passing

over the low ground of Marden Park. The embankment is

about 1,200 feet in length, and is connected at the southern end

with a long but not very deep cutting, which extends to the

northern mouth of the long tunnel under the higher ridges of the

North Downs.

The cutting (No. XIII.) is the last on this line of railway in

which the chalk of the North Downs is exposed. It is 2,770

feet in length, and follows a meandering course, but the general

direction is nearly north and south. It also varies in depth, in

one place not being more than twelve feet deep, while at the

tunnel mouth it presents a vertical section of thirty-four feet.

The greater part of this cutting has been smoothed down. The

beds are only seen in a rough state in three places, namely: 1stly.

For a short length near the north end of the cutting, where

rubbly chalk is seen, with a few beds of thicker and firmer chalk,

and some irregular and thin bands of marl. 2ndly. A small

part of the cutting has been left in a rough state at a spot where

a temporary bridge over the cutting has been erected. Here

there is a section eighteen feet deep, shpwing white chalk, in

rather thick beds near the bottom and more rubbly above, and

at the height of six feet there is a very conspicuoul band of

brown and yellow marl, the bedding of which is irregular.

Lastly, for the length of 600 feet at the south end of the cutting,

near the tunnel mouth, a fine section is exposed. This section

shows a perceptible but not a very great inclination of the beds

to the north. Within and above the tunnel mouth are beds

of chalk, averaging .about two feet six inches in thickness,

separated by lines of division. These lines of division are in

some places filled with a brownish earth. Specimens of inoceramus

are occasionally seen on the under side of the beds of chalk above

25

the 'partings. Outside the mouth of the tunnel the lines of

bedding undulate irregnlarly. The upper part of the section is

not so clearly exposed, being masked by fallen portions of and

the wash from the superficial deposit, which here consists of

about three feet of brownish marl containing a few broken flints

and many fragments of chalk.

The most interesting deposit in this section is a band of

chalk about four feet in thickness, which is crowded with frag­

ments of shells, together with some which are entire. At the

distance of 160 feet from the mouth of the tunnel, the upper

part of this shelly band is at the height of eighteen feet.

It dips regularly towards the north, and at 460 feet from the

tunnel mouth, the top of the bed is not more than six feet above

the level of the railway. At this spot the continuity of the beds

is broken by a well marked fault, which has a slope towards the

south. This fault has caused a displacement of the beds to the

extent of more than two feet. On the south side of the fault

the top of the shell bed is at the height of six feet, and on

the north side it is at eight feet four inches. For a dis­

tance of fifteen feet on the north side of the fault the strata are

slightly inclined towards it. At some spots a band of brown

clayey marl, or ochre, containing iron pyrites, is seen immedi­

ately above the shell bed. Although the fossils contained in

this stratum are very numerous, only a few species are repre­

sented. By far the most abundant fossil is Inoceramus myti­

loides, which may be obtained in great numbers. The Echino­

derms are represented by a depressed form of Galel'ites, and by

Discoidea subuculus; the Brachiopods by Rhynchonella Cuviel'i,

Terebratula obesa, and others.On the snrface of the embankment, at the northern end of

this cutting, and in the cntting and on the embankment yet

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26

further to the north, are many blocks of chalk which are crowded

with Inoceramus mytiloides. These blocks were probably derived

from this shell bed.

On the embankment the casts of large Ammonites are occa­

sionally met with. They are mostly in a broken condition, but

one very fine one which I measured was eighteen inches in

longest diameter. These AJmmonites approach nearest to Ammonites

peramplus of Mantell. The position in the section which these

fine fossils occupied when in situ is uncertain. They are inter­

esting as having been probably derived from the highest Ammo­

nite-bearing bed of the chalk of the line of sections under

consideration.

LOWER MARDEN PARK BEDs.-The last mentioned cutting is

the most southerly one in which an open section of the chalk is

seen. From this point a long tunnel under the Downs has been

partly formed, and the nature of the beds intervening between

the chalk before described and the firestone and gault can only

be ascertained by examining the spoil-heaps around the shafts

on the hills above the tunnel.

This tunnel is about 7,200 feet in length. The shafts, ten in

number, are sunk at intervals varying from about 450 to 1,100

feet.There are three shafts between the north mouth of the tunnel

and the top of the first ridge above it; one on the southern

slope of this ridge, three on the northern slope of the main escarp­

ment, and three in the comparatively low ground to the south of it.

Around the four northernmost shafts much of the spoil con­

sists of hard white chalk, differing but little from the lowest

beds in the cutting at the north mouth of the tunnel, and de­

rived probably from the extension of the same beds. This chalk

contains very few organic remains.

27

At the two shafts. on the north slope of the first ridge there

are also many blocks of hard white and yellow chalk, which con­

tain lumpy concretions of a greyish colour, and also a few blocks

of yellow chalk, containing an Exogyra. Other masses of yellow

marly chalk contain casts of a small Inoceramus, and occasionally

Terebratula obesa and Belemnitella plena.

The three shafts to the south of the four before noticed show

masses of earthy dark grey chalk marl, and also blocks of

yellowish chalk.The light grey and yellowish chalk is hard and shows little

approach to marl; it contains in abundance casts of Ammonites

varians and of Inocel'amus.

The dark grey blocks are very marly in character, and on the

surface of the spoil-heap are often disintegrated. They con­

tain casts of Ammonites and Inoceramus, and occasionally casts of

Pleurotomal'ia and Littorina (?). These. dark blocks on being

split also show small patches of a black, a red, or an ochreous tint.

Some of these patches are irregular in form, but others closely

resemble the casts or impressions of small bivalves. The shaft,

at which these fossils are found, is the last one on the north side

of the escarpment of the North Downs.

On the edge of the escarpment at the highest point there

is a considerable amount of surface deposit, a section of which

is seen in a small cutting near the top of the hill excavated

for the purpose of forming an uniform slope up which to

raise materials from the lower ground. Above beds of chalk

without layers of flints, there is at this spot about three feet

of rubbly chalk succeeded by about ten feet of brown marly

clay, darker in colour towards the base, and containing in the

lower portion small lumps of chalk and in the upper part lumps

of chalk, together with fragments of flints. The layers of this

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28

marl appear to slope in a south-easterly direction; above this de­

posit is a thin layer of rubbly chalk, and then about one foot of

light brown marl, which extends to the surface.

The southern slope of the escarpment descends at a very steep

angle for a distance of 570 feet, from which spot the surface

slopes more gently for about 1,300 feet. At this last point the

south mouth of the tunnel is situated.

On this comparatively low ground three shafts have been sunk,

the first at the foot of the steep escarpment, the second 670 feet

south of the first, the third 580 feet from the second, and about

80 feet from the tunnel mouth. Only a small amount of debris

is seen around these three shafts, but at each there is a bluish

marly clay, resembling the gault, and containing small phos­

phatic nodules, and nodules of iron pyrites; but I h~;'e not

found any fossils in this deposit.

At the two shafts wwch are nearest to the escarpment a few

blocks of calcareous sandstone are seen, similar in mineral char­

acter to the rock known as the firestone, which is extensively

quarried a few miles to the west, on the road between Caterham

and Godstone, and also in the neighbourhood of Reigate, and is

the representative in Surrey of the Upper,Greensand of the Isle

of Wight and of Wiltshire. It may, therefore, be inferred that

the Upper Greensand is present in this section, but so little ex­

cavation has been made that any attempt to determine the thick­

ness and importance of this deposit here would be prematurE'.

From the south mouth of the tunnel a cutting (No. XIV.)

extends for about 500 feet. It is 27 feet in depth at the northern

end, and has been formed in a blue marly clay, similar to that

seen around the adjacent shafts. Near the surface this marl

becomes of a light brownish colour, and in the upper part con­

tains small lumps of chalk. Towards the south end of the cut-

29

ting there is a surface deposit of grey earth containing small

lumps of chalk and also broken flints. I have obtained no fos­sils from this cutting.

Oxtead Church is situated at a short distance further to the south.

DISTRIBUTION OF FOSSILS.

In the previous part of this paper I have given a general de­

scription of the various sections of the chalk seen on the Surrey

and Sussex Railway between Croydon and Oxtead. I have now

to consider the distribution of the fossils in the various beds

along this line. For this purpose I subjoin a list of the fossils

obtained from this line of sections, which I have been able toidentify.

The columns of the following table I have headed with the

locftlities from which I have obtained distinct groups of fossils.

Two columns are assigned to the Purley Chalk, the first denot­

ing the fossils from the cuttings adjacent to Purley (Nos. I., 11.,IlL), and the second those from the cutting (No. IV.) at the

north mouth of the Riddlesdown tunnel, where slightly lower

beds are present. The next column gives the fossils obtained

from the shafts of the tunnel under Riddlesdown. The column

headed Upper Kenley shows the fossils from the cutting (No.

V.) at the south mouth of the same tunnel. Lower Kenley,

the fossils from the cutting (No. VI.) north of the Rose and

Crown. Whiteleaf, those from the cuttings (Nos. VIL, VIIL,

IX., X., XI.) between the Rose and Crown and the lateral

valley north of Marden Park. Upper Marden Park, the fossils

from the cuttings (Nos. XIL, XIII.), and Lower Marden Park

those from the shafts of the tunnel adjacent to that Park.

I have denoted by an asterisk the fossils which are present, by

a C those that are common, and by an A those which are very

abundant in each of these localities.

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